docs(aio): update migrated content from anguar.io

aio/content/examples/reactive-forms/src/app/app.component.ts

@@ -0,0 +1,12 @@
+// #docregion
+import { Component } from '@angular/core';
+
+@Component({
+  selector: 'my-app',
+  template: `
+  <div class="container">
+    <h1>Reactive Forms</h1>
+    <hero-list></hero-list>
+  </div>`
+})
+export class AppComponent { }