docs(angular): adds docs to angular API (#17211)

angular/src/util/overlay.ts

@@ -3,14 +3,23 @@ import { proxyMethod } from './util';
 export class OverlayBaseController<Opts, Overlay> {
   constructor(private ctrl: string) {}
 
+  /**
+   * Creates a new overlay
+   */
   create(opts?: Opts): Promise<Overlay> {
     return proxyMethod(this.ctrl, 'create', opts);
   }
 
+  /**
+   * When `id` is not provided, it dismisses the top overlay.
+   */
   dismiss(data?: any, role?: string, id?: string): Promise<void> {
     return proxyMethod(this.ctrl, 'dismiss', data, role, id);
   }
 
+  /**
+   * Returns the top overlay.
+   */
   getTop(): Promise<Overlay> {
     return proxyMethod(this.ctrl, 'getTop');
   }