docs: refresh TypeScript configuration guide with updated info and files (#31097)

This removes the hard-coded tsconfig.json to use a separate file.
The tsconfig.0.json is added to the getting-started example folder
because have to check it with every major release
Also updates the text regarding defaults for TypeScript compilation targets
and typings

PR Close #31097

aio/content/examples/getting-started/tsconfig.0.json

@@ -0,0 +1,29 @@
+// This tsconfig is used in the TypeScript
+// configuration guide (../guide/typescript-configuration.md) 
+// to display the latest default configuration
+// Note: Update with every major release to the latest default
+// #docregion
+{
+  "compileOnSave": false,
+  "compilerOptions": {
+    "baseUrl": "./",
+    "outDir": "./dist/out-tsc",
+    "sourceMap": true,
+    "declaration": false,
+    "module": "esnext",
+    "moduleResolution": "node",
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "importHelpers": true,
+    "target": "es2015",
+    "typeRoots": [
+      "node_modules/@types"
+    ],
+// #docregion lib    
+    "lib": [
+      "es2018",
+      "dom"
+    ]
+// #enddocregion lib
+  }
+}

aio/content/guide/typescript-configuration.md

@@ -23,31 +23,14 @@ guide the compiler as it generates JavaScript files.
 
 <div class="alert is-helpful">
 
-
-
 For details about `tsconfig.json`, see the official
 [TypeScript wiki](http://www.typescriptlang.org/docs/handbook/tsconfig-json.html).
 
 </div>
 
+The [Setup](guide/setup-local) guide uses the following `tsconfig.json`:
 
-
-The [Setup](guide/setup) guide uses the following `tsconfig.json`:
-
-<code-example lang="json" header="tsconfig.json" linenums="false">
-  {
-    "compilerOptions": {
-      "target": "es5",
-      "module": "commonjs",
-      "moduleResolution": "node",
-      "sourceMap": true,
-      "emitDecoratorMetadata": true,
-      "experimentalDecorators": true,
-      "lib": [ "es2015", "dom" ],
-      "noImplicitAny": true,
-      "suppressImplicitAnyIndexErrors": true
-    }
-  }
+<code-example path="getting-started/tsconfig.0.json" header="tsconfig.json" linenums="false">
 </code-example>
 
 This file contains options and flags that are essential for Angular applications.
@@ -66,7 +49,6 @@ When the `noImplicitAny` flag is `false` (the default), and if
 the compiler cannot infer the variable type based on how it's used,
 the compiler silently defaults the type to `any`. That's what is meant by *implicit `any`*.
 
-The documentation setup sets the `noImplicitAny` flag to `true`.
 When the `noImplicitAny` flag is `true` and the TypeScript compiler cannot infer
 the type, it still generates the JavaScript files, but it also **reports an error**.
 Many seasoned developers prefer this stricter setting because type checking catches more
@@ -79,20 +61,15 @@ Most developers feel that *this particular error* is more annoying than helpful.
 You can suppress them with the following additional flag:
 
 <code-example format=".">
-  "suppressImplicitAnyIndexErrors":true
+
+  "suppressImplicitAnyIndexErrors": true
 
 </code-example>
 
-
-
-The documentation setup sets this flag to `true` as well.
-
-
 {@a typings}
 
-
-
 ## TypeScript Typings
+
 Many JavaScript libraries, such as jQuery, the Jasmine testing library, and Angular,
 extend the JavaScript environment with features and syntax
 that the TypeScript compiler doesn't recognize natively.
@@ -116,20 +93,13 @@ TypeScript includes a special declaration file called `lib.d.ts`. This file cont
 Based on the `--target`, TypeScript adds _additional_ ambient declarations
 like `Promise` if the target is `es6`.
 
-Since the QuickStart is targeting `es5`, you can override the
-list of declaration files to be included:
-
-
-<code-example format=".">
-  "lib": ["es2015", "dom"]
+By default, the target is `es2015`. If you are targeting `es5`, you still have newer type declarations due to the list of declaration files included:
 
+<code-example path="getting-started/tsconfig.0.json" header="tsconfig.json (lib excerpt)" linenums="false" region="lib">
 </code-example>
 
-
-
-Thanks to that, you have all the `es6` typings even when targeting `es5`.
-
 ### Installable typings files
+
 Many libraries&mdash;jQuery, Jasmine, and Lodash among them&mdash;do *not* include `d.ts` files in their npm packages.
 Fortunately, either their authors or community contributors have created separate `d.ts` files for these libraries and
 published them in well-known locations.
@@ -138,17 +108,7 @@ You can install these typings via `npm` using the
 [`@types/*` scoped package](http://www.typescriptlang.org/docs/handbook/declaration-files/consumption.html)
 and Typescript, starting at 2.0, automatically recognizes them.
 
-For instance, to install typings for `jasmine` you could do `npm install @types/jasmine --save-dev`.
-
-
-QuickStart identifies two *typings*, or `d.ts`, files:
-
-* [jasmine](http://jasmine.github.io/) typings for the Jasmine test framework.
-
-* [node](https://www.npmjs.com/package/@types/node) for code that references objects in the *Node.js®* environment;
-
-
-QuickStart doesn't require these typings but many of the samples do.
+For instance, to install typings for `jasmine` you run `npm install @types/jasmine --save-dev`.
 
 
 {@a target}
@@ -156,5 +116,4 @@ QuickStart doesn't require these typings but many of the samples do.
 
 ### *target*
 
-By default, the target is `es5`, you can configure the target to `es6` if you only want to deploy the application to
-es6 compatible browser. But if you configure the target to `es6` in some old browser such as `IE`, `Syntax Error` will be thrown.
+By default, the target is `es2015`, which is supported only in modern browsers. You can configure the target to `es5` to specifically support legacy browsers. [Differential loading](guide/deployment#differential-loading) is also provided by the Angular CLI to support modern, and legacy browsers with separate bundles.