fix(docs-infra): use relative URLs for internal links on error pages (#40881)

Previously, some of the links on the error pages had URLs prefixed with
`https://angular.io/`. This caused them to be treated as external URLs,
which had the following downsides:
- Links would always point to `angular.io` instead of the same version
  as the error page (e.g. `next.angular.io` or `v11.angular.io`).
- Dgeni would not be able to check that the URLs are valid (i.e. point
  to existing pages).
- An external link icon would incorrectly be shown next to the links on
  `angular.io`.

This commit fixes the links to use relative URLs.

PR Close #40881

aio/content/errors/NG0100.md

@@ -4,7 +4,7 @@
 @shortDescription Expression has changed after it was checked
 
 @description
-Angular throws an `ExpressionChangedAfterItHasBeenCheckedError` when an expression value has been changed after change detection has completed. Angular only throws this error in development mode. 
+Angular throws an `ExpressionChangedAfterItHasBeenCheckedError` when an expression value has been changed after change detection has completed. Angular only throws this error in development mode.
 
 In dev mode, Angular performs an additional check after each change detection run, to ensure the bindings haven’t changed. This catches errors where the view is left in an inconsistent state. This can occur, for example, if a method or getter returns a different value each time it is called, or if a child component changes values on its parent. If either of these occur, this is a sign that change detection is not stabilized. Angular throws the error to ensure data is always reflected correctly in the view, which prevents erratic UI behavior or a possible infinite loop.
 
@@ -13,8 +13,8 @@ This error commonly occurs when you’ve added template expressions or begun to
 @debugging
 The [source maps](https://developer.mozilla.org/en-US/docs/Tools/Debugger/How_to/Use_a_source_map) generated by the CLI are very useful when debugging. Navigate up the call stack until you find a template expression where the value displayed in the error has changed.
 
-Ensure that there are no changes to the bindings in the template after change detection is run. This often means refactoring to use the correct [component lifecycle hook](https://angular.io/guide/lifecycle-hooks) for your use case. If the issue exists within `ngAfterViewInit`, the recommended solution is to use a constructor or `ngOnInit` to set initial values, or use `ngAfterContentInit` for other value bindings.
+Ensure that there are no changes to the bindings in the template after change detection is run. This often means refactoring to use the correct [component lifecycle hook](guide/lifecycle-hooks) for your use case. If the issue exists within `ngAfterViewInit`, the recommended solution is to use a constructor or `ngOnInit` to set initial values, or use `ngAfterContentInit` for other value bindings.
 
-If you are binding to methods in the view, ensure that the invocation does not update any of the other bindings in the template. 
+If you are binding to methods in the view, ensure that the invocation does not update any of the other bindings in the template.
 
-Read more about which solution is right for you in ['Everything you need to know about the "ExpressionChangedAfterItHasBeenCheckedError" error'](https://indepth.dev/everything-you-need-to-know-about-the-expressionchangedafterithasbeencheckederror-error/) and why this is useful at ['Angular Debugging "Expression has changed after it was checked": Simple Explanation (and Fix)'](https://blog.angular-university.io/angular-debugging/).
+Read more about which solution is right for you in ['Everything you need to know about the "ExpressionChangedAfterItHasBeenCheckedError" error'](https://indepth.dev/everything-you-need-to-know-about-the-expressionchangedafterithasbeencheckederror-error/) and why this is useful at ['Angular Debugging "Expression has changed after it was checked": Simple Explanation (and Fix)'](https://blog.angular-university.io/angular-debugging/).

aio/content/errors/NG0200.md

@@ -4,9 +4,9 @@
 @shortDescription Circular dependency in DI detected while instantiating a provider
 
 @description
-A cyclic dependency exists when a [dependency of a service](https://angular.io/guide/hierarchical-dependency-injection) directly or indirectly depends on the service itself. For example, if `UserService` depends on `EmployeeService`, which also depends on `UserService`. Angular will have to instantiate `EmployeeService` to create `UserService`, which depends on `UserService`, itself.
+A cyclic dependency exists when a [dependency of a service](guide/hierarchical-dependency-injection) directly or indirectly depends on the service itself. For example, if `UserService` depends on `EmployeeService`, which also depends on `UserService`. Angular will have to instantiate `EmployeeService` to create `UserService`, which depends on `UserService`, itself.
 
 @debugging
-Use the call stack to determine where the cyclical dependency exists. You will be able to see if any child dependencies rely on the original file by [mapping out](https://angular.io/guide/dependency-injection-in-action) the component, module, or service’s dependencies and identify the loop causing the problem.
+Use the call stack to determine where the cyclical dependency exists. You will be able to see if any child dependencies rely on the original file by [mapping out](guide/dependency-injection-in-action) the component, module, or service’s dependencies and identify the loop causing the problem.
 
 Break this loop (or circle) of dependency to resolve this error. This most commonly means removing or refactoring the dependencies to not be reliant on one another.

aio/content/errors/NG0201.md

@@ -4,12 +4,12 @@
 @shortDescription No provider for {token} found!
 
 @description
-You see this error when you try to inject a service but have not declared a corresponding provider. A provider is a mapping that supplies a value that you can inject into the constructor of a class in your application. 
+You see this error when you try to inject a service but have not declared a corresponding provider. A provider is a mapping that supplies a value that you can inject into the constructor of a class in your application.
 
-Read more on providers in our [Dependency Injection guide](https://angular.io/guide/dependency-injection).
+Read more on providers in our [Dependency Injection guide](guide/dependency-injection).
 
 @debugging
-Work backwards from the object where the error states that a [provider](https://angular.io/guide/architecture-services) is missing: `No provider for ${this}!`. This is commonly thrown in [services](https://angular.io/tutorial/toh-pt4), which require non-existing providers.  
+Work backwards from the object where the error states that a [provider](guide/architecture-services) is missing: `No provider for ${this}!`. This is commonly thrown in [services](tutorial/toh-pt4), which require non-existing providers.
 
 To fix the error ensure that your service is registered in the list of providers of an `NgModule` or has the `@Injectable` decorator with a `providedIn` property at top.
 
@@ -17,4 +17,4 @@ The most common solution is to add a provider in `@Injectable` using `providedIn
 
 ```typescript
 @Injectable({ providedIn: 'app' })
-```
+```

aio/content/errors/NG0300.md

@@ -1,13 +1,13 @@
-@name Selector Collision 
+@name Selector Collision
 @category runtime
 @videoUrl https://www.youtube.com/embed/z_3Z5mOm59I
 @shortDescription Multiple components match with the same tagname
 
 @description
-Two or more components use the same [element selector](https://angular.io/guide/component-overview#specifying-a-components-css-selector). Because there can only be a single component associated with an element, selectors must be unique strings to prevent ambiguity for Angular.
+Two or more components use the same [element selector](guide/component-overview#specifying-a-components-css-selector). Because there can only be a single component associated with an element, selectors must be unique strings to prevent ambiguity for Angular.
 
 @debugging
-Use the element name from the error message to search for places where you’re using the same [selector declaration](https://angular.io/guide/architecture-components) in your codebase:
+Use the element name from the error message to search for places where you’re using the same [selector declaration](guide/architecture-components) in your codebase:
 
 ```typescript
 @Component({
@@ -18,4 +18,4 @@ Use the element name from the error message to search for places where you’re
 
 Ensure that each component has a unique CSS selector. This will guarantee that Angular renders the component you expect.
 
-If you’re having trouble finding multiple components with this selector tag name, check for components from imported component libraries, such as Angular Material. Make sure you're following the [best practices](https://angular.io/guide/styleguide#component-selectors) for your selectors to prevent collisions.
+If you’re having trouble finding multiple components with this selector tag name, check for components from imported component libraries, such as Angular Material. Make sure you're following the [best practices](guide/styleguide#component-selectors) for your selectors to prevent collisions.

aio/content/errors/NG0301.md

@@ -4,7 +4,7 @@
 @shortDescription Export not found!
 
 @description
-Angular can’t find a directive with `{{ PLACEHOLDER }}` export name. The export name is specified in the `exportAs` property of the directive decorator. This is common when using FormsModule or Material modules in templates, and you’ve forgotten to [import the corresponding modules](https://angular.io/guide/sharing-ngmodules).
+Angular can’t find a directive with `{{ PLACEHOLDER }}` export name. The export name is specified in the `exportAs` property of the directive decorator. This is common when using FormsModule or Material modules in templates, and you’ve forgotten to [import the corresponding modules](guide/sharing-ngmodules).
 
 <div class="alert is-helpful">
 
@@ -15,7 +15,7 @@ This is the runtime equivalent of a common compiler error [NG8003: No directive
 @debugging
 Use the export name to trace the templates or modules using this export.
 
-Ensure that all dependencies are [properly imported and declared in your NgModules](https://angular.io/guide/sharing-ngmodules). For example, if the export not found is `ngForm`, we need to import `FormsModule` and declare it in the list of imports in `*.module.ts` to resolve the error. 
+Ensure that all dependencies are [properly imported and declared in your NgModules](guide/sharing-ngmodules). For example, if the export not found is `ngForm`, we need to import `FormsModule` and declare it in the list of imports in `*.module.ts` to resolve the error.
 
 ```typescript
 import { FormsModule } from '@angular/forms';

aio/content/errors/NG2003.md

@@ -3,9 +3,9 @@
 @shortDescription No suitable injection token for parameter
 
 @description
-There is no injection token for a constructor parameter at compile time. [InjectionTokens](https://angular.io/api/core/InjectionToken) are tokens that can be used in a Dependency Injection Provider.
+There is no injection token for a constructor parameter at compile time. [InjectionTokens](api/core/InjectionToken) are tokens that can be used in a Dependency Injection Provider.
 
 @debugging
 Look at the parameter that throws the error and all uses of the class. This error is commonly thrown when a constructor defines parameters with primitive types like `string`, `number`, `boolean`, and `Object`.
 
-Use the [@Injectable](https://angular.io/api/core/Injectable) method or [@Inject](https://angular.io/api/core/Inject) decorator from `@angular/core` to ensure that the type you are injecting is reified (has a runtime representation). Make sure to add a provider to this decorator so that you do not throw [NG0201: No Provider Found](https://angular.io/errors/NG0201).
+Use the [@Injectable](api/core/Injectable) method or [@Inject](api/core/Inject) decorator from `@angular/core` to ensure that the type you are injecting is reified (has a runtime representation). Make sure to add a provider to this decorator so that you do not throw [NG0201: No Provider Found](errors/NG0201).

aio/content/errors/NG8001.md

@@ -12,10 +12,10 @@ This is the compiler equivalent of a common runtime error `NG0304: '${tagName}'
 </div>
 
 @debugging
-Use the element name in the error to find the file(s) where the element is being used. 
+Use the element name in the error to find the file(s) where the element is being used.
 
-Check that the name and selector are correct. If the component is from a different module or import, check that the component is exported from its origin module and imported into the correct `*.modules.ts` file, and declared in the imports list. 
+Check that the name and selector are correct. If the component is from a different module or import, check that the component is exported from its origin module and imported into the correct `*.modules.ts` file, and declared in the imports list.
 
-When using custom elements or web components, ensure that you add [`CUSTOM_ELEMENTS_SCHEMA`](https://angular.io/api/core/CUSTOM_ELEMENTS_SCHEMA) to the app module.
+When using custom elements or web components, ensure that you add [`CUSTOM_ELEMENTS_SCHEMA`](api/core/CUSTOM_ELEMENTS_SCHEMA) to the app module.
 
 If this does not resolve the error, check the imported libraries for any recent changes to the exports and properties you are using, and restart your server.

aio/content/errors/NG8002.md

@@ -13,4 +13,4 @@ This error arises when attempting to bind to a property that does not exist. Any
 The runtime error for this is `NG0304: '${tagName}' is not a known element: …’`.
 
 @debugging
-Look at documentation for the specific [binding syntax](https://angular.io/guide/binding-syntax) used. This is usually a typo or incorrect import. There may also be a missing direction with property selector ‘name’ or missing input.
+Look at documentation for the specific [binding syntax](guide/binding-syntax) used. This is usually a typo or incorrect import. There may also be a missing direction with property selector ‘name’ or missing input.

aio/content/errors/NG8003.md

@@ -4,7 +4,7 @@
 @shortDescription No directive found with export
 
 @description
-Angular can’t find a directive with `{{ PLACEHOLDER }}` export name. This is common with a missing import or a missing [`exportAs`](https://angular.io/api/core/Directive#exportAs) on a directive.
+Angular can’t find a directive with `{{ PLACEHOLDER }}` export name. This is common with a missing import or a missing [`exportAs`](api/core/Directive#exportAs) on a directive.
 
 
 <div class="alert is-helpful">
@@ -16,7 +16,7 @@ This is the compiler equivalent of a common runtime error [NG0301: Export Not Fo
 @debugging
 Use the string name of the export not found to trace the templates or modules using this export.
 
-Ensure that all dependencies are properly imported and declared in our Modules. For example, if the export not found is `ngForm`, we will need to import `FormsModule` and declare it in our list of imports in `*.module.ts` to resolve the missing export error. 
+Ensure that all dependencies are properly imported and declared in our Modules. For example, if the export not found is `ngForm`, we will need to import `FormsModule` and declare it in our list of imports in `*.module.ts` to resolve the missing export error.
 
 ```typescript
 import { FormsModule } from '@angular/forms';