refactor: fix undecorated classes with angular features in repo (#36921)

A few instances of undecorated classes with Angular features
have been discovered in the framework repo. This commit fixes
those.

PR Close #36921

aio/content/examples/lifecycle-hooks/src/app/peek-a-boo.component.ts

@@ -3,6 +3,7 @@ import {
   AfterContentInit,
   AfterViewChecked,
   AfterViewInit,
+  Directive,
   DoCheck,
   OnChanges,
   OnDestroy,
@@ -15,7 +16,8 @@ import { LoggerService }    from './logger.service';
 let nextId = 1;
 
 // #docregion ngOnInit
-export class PeekABoo implements OnInit {
+@Directive()
+export class PeekABooDirective implements OnInit {
   constructor(private logger: LoggerService) { }
 
   // implement OnInit's `ngOnInit` method
@@ -34,7 +36,7 @@ export class PeekABoo implements OnInit {
 })
 // Don't HAVE to mention the Lifecycle Hook interfaces
 // unless we want typing and tool support.
-export class PeekABooComponent extends PeekABoo implements
+export class PeekABooComponent extends PeekABooDirective implements
              OnChanges, OnInit, DoCheck,
              AfterContentInit, AfterContentChecked,
              AfterViewInit, AfterViewChecked,