docs: clean up docregions in the `getting-started` docs example (#40197)

This commit does some minor clean-up in docregions of the
`getting-started` docs example. More specifically, it:
- Removes redundant docregion markers.
- Fixes whitespace inconsistencies.
- Adds `/* ... */` to indicate that there is more code before the end of
  a docregion (in order to avoid confusion).

PR Close #40197

aio/content/examples/getting-started/src/app/product-details/product-details.component.1.ts

@@ -11,7 +11,7 @@ import { products } from '../products';
   templateUrl: './product-details.component.html',
   styleUrls: ['./product-details.component.css']
 })
-// #docregion props-methods, add-to-cart, product-prop
+// #docregion props-methods, product-prop
 export class ProductDetailsComponent implements OnInit {
   product;
   // #enddocregion product-prop
@@ -29,9 +29,9 @@ export class ProductDetailsComponent implements OnInit {
     this.product = products.find(product => {
       return product.id === Number(productIdFromRoute);
     });
-  // #docregion product-prop
   }
-  // #enddocregion product-prop
   // #enddocregion get-product
+  // #docregion product-prop
+  /* ... */
   // #docregion props-methods
 }

aio/content/examples/getting-started/src/app/product-details/product-details.component.ts

@@ -13,9 +13,9 @@ import { CartService } from '../cart.service';
   templateUrl: './product-details.component.html',
   styleUrls: ['./product-details.component.css']
 })
-// #docregion props-methods, get-product, inject-cart-service, add-to-cart
+// #docregion props-methods, inject-cart-service, add-to-cart
 export class ProductDetailsComponent implements OnInit {
-// #enddocregion add-to-cart, get-product, inject-cart-service
+// #enddocregion add-to-cart, inject-cart-service
   product;
 
 // #docregion inject-cart-service
@@ -27,7 +27,6 @@ export class ProductDetailsComponent implements OnInit {
   ) { }
 // #enddocregion inject-cart-service
 
-// #docregion get-product
   ngOnInit() {
 // #enddocregion props-methods
     // First get the product id from the current route.
@@ -39,11 +38,11 @@ export class ProductDetailsComponent implements OnInit {
 // #docregion props-methods
   }
 
-// #enddocregion props-methods, get-product
+// #enddocregion props-methods
 // #docregion add-to-cart
   addToCart(product) {
     this.cartService.addToCart(product);
     window.alert('Your product has been added to the cart!');
   }
-// #docregion props-methods, get-product, inject-cart-service
+// #docregion props-methods, inject-cart-service
 }

aio/content/examples/getting-started/src/app/product-list/product-list.component.html

@@ -8,7 +8,8 @@
       {{ product.name }}
     </a>
   </h3>
-<!-- #enddocregion router-link -->  
+
+  <!-- #enddocregion router-link -->
   <p *ngIf="product.description">
     Description: {{ product.description }}
   </p>
@@ -21,6 +22,7 @@
     [product]="product"
     (notify)="onNotify()">
   </app-product-alerts>
-<!-- #docregion router-link -->
+  <!-- #docregion router-link -->
+
 </div>
 <!-- #enddocregion router-link -->