feat(test): add challenge 18 and 19 avout testing

apps/testing-input-output/src/app/app.component.ts

@@ -0,0 +1,13 @@
+import { NxWelcomeComponent } from './nx-welcome.component';
+import { Component } from '@angular/core';
+
+@Component({
+  standalone: true,
+  imports: [NxWelcomeComponent],
+  selector: 'app-root',
+  template: ` <app-nx-welcome></app-nx-welcome> `,
+  styles: [],
+})
+export class AppComponent {
+  title = 'testing-input-output';
+}