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

PR Close #20306

aio/content/examples/ngmodule-faq/src/main.1.ts

@@ -0,0 +1,11 @@
+import { enableProdMode } from '@angular/core';
+import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
+
+import { AppModule } from './app/app.module.1';
+import { environment } from './environments/environment';
+
+if (environment.production) {
+  enableProdMode();
+}
+
+platformBrowserDynamic().bootstrapModule(AppModule);