docs(aio): add NgModule docs (#20306)

PR Close #20306

aio/content/examples/ngmodule-faq/src/app/app.module.ts

@@ -0,0 +1,39 @@
+// #docplaster
+// #docregion
+// #docregion v4
+/* Angular Imports */
+import { NgModule }       from '@angular/core';
+import { BrowserModule }  from '@angular/platform-browser';
+
+/* App Imports */
+import { AppComponent }   from './app.component';
+
+/* Core Modules */
+import { CoreModule }       from './core/core.module';
+
+/* Routing Module */
+import { AppRoutingModule } from './app-routing.module';
+
+@NgModule({
+  // #docregion import-for-root
+  imports: [
+    BrowserModule,
+// #enddocregion v4
+// #enddocregion import-for-root
+/*
+// #docregion v4
+    CoreModule,
+// #enddocregion v4
+*/
+// #docregion import-for-root
+    CoreModule.forRoot({userName: 'Miss Marple'}),
+// #docregion v4
+    AppRoutingModule
+  ],
+  // #enddocregion import-for-root
+  declarations: [ AppComponent ],
+  bootstrap:    [ AppComponent ]
+})
+export class AppModule { }
+// #enddocregion v4
+// #enddocregion