refactor(docs-infra): fix docs examples for Angular-specific tslint rules (#38143)

This commit updates the docs examples to be compatible with the
following Angular-specific tslint rules:
- `component-selector`
- `directive-selector`
- `no-conflicting-lifecycle`
- `no-host-metadata-property`
- `no-input-rename`
- `no-output-native`
- `no-output-rename`

This is in preparation of updating the docs examples `tslint.json` to
match the one generated for new Angular CLI apps in a future commit.

PR Close #38143

aio/content/examples/observables-in-angular/src/main.ts

@@ -1,11 +1,12 @@
-
+// tslint:disable: no-output-native
+// #docregion
 import { Component, Output, OnInit, EventEmitter, NgModule } from '@angular/core';
 import { Observable } from 'rxjs';
 
 // #docregion eventemitter
 
 @Component({
-  selector: 'zippy',
+  selector: 'app-zippy',
   template: `
     <div class="zippy">
       <div (click)="toggle()">Toggle</div>