build(aio): change examples to CLI (#19248)

PR Close #19248

aio/content/examples/user-input/src/main.ts

@@ -1,5 +1,11 @@
+import { enableProdMode } from '@angular/core';
 import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
 
 import { AppModule } from './app/app.module';
+import { environment } from './environments/environment';
+
+if (environment.production) {
+  enableProdMode();
+}
 
 platformBrowserDynamic().bootstrapModule(AppModule);