docs(core): add an example of configuring APP_INITIALIZER token in co…

…ntext of standalone components (#52084)

docs(core): fix formatting

PR Close #52084

packages/core/src/application_init.ts

@@ -31,7 +31,7 @@ import {isPromise, isSubscribable} from './util/lang';
  *
  * The following example illustrates how to configure a multi-provider using `APP_INITIALIZER` token
  * and a function returning a promise.
- *
+ * ### Example with NgModule-based application
  * ```
  *  function initializeApp(): Promise<any> {
  *    return new Promise((resolve, reject) => {
@@ -53,11 +53,38 @@ import {isPromise, isSubscribable} from './util/lang';
  *  export class AppModule {}
  * ```
  *
+ * ### Example with standalone application
+ * ```
+ * export function initializeApp(http: HttpClient) {
+ *   return (): Promise<any> =>
+ *     firstValueFrom(
+ *       http
+ *         .get("https://someUrl.com/api/user")
+ *         .pipe(tap(user => { ... }))
+ *     );
+ * }
+ *
+ * bootstrapApplication(App, {
+ *   providers: [
+ *     provideHttpClient(),
+ *     {
+ *       provide: APP_INITIALIZER,
+ *       useFactory: initializeApp,
+ *       multi: true,
+ *       deps: [HttpClient],
+ *     },
+ *   ],
+ * });
+
+ * ```
+ *
+ *
  * It's also possible to configure a multi-provider using `APP_INITIALIZER` token and a function
  * returning an observable, see an example below. Note: the `HttpClient` in this example is used for
  * demo purposes to illustrate how the factory function can work with other providers available
  * through DI.
  *
+ * ### Example with NgModule-based application
  * ```
  *  function initializeAppFactory(httpClient: HttpClient): () => Observable<any> {
  *   return () => httpClient.get("https://someUrl.com/api/user")
@@ -80,6 +107,27 @@ import {isPromise, isSubscribable} from './util/lang';
  *  export class AppModule {}
  * ```
  *
+ * ### Example with standalone application
+ *
+ *  function initializeAppFactory(httpClient: HttpClient): () => Observable<any> {
+ *   return () => httpClient.get("https://someUrl.com/api/user")
+ *     .pipe(
+ *        tap(user => { ... })
+ *     );
+ *  }
+ *
+ * bootstrapApplication(App, {
+ *   providers: [
+ *     provideHttpClient(),
+ *     {
+ *       provide: APP_INITIALIZER,
+ *       useFactory: initializeApp,
+ *       multi: true,
+ *       deps: [HttpClient],
+ *     },
+ *   ],
+ * });
+ *
  * @publicApi
  */
 export const APP_INITIALIZER =