fix(build): test example directories with unit and e2e tests (#11296)

modules/@angular/examples/_common/module.d.ts

@@ -0,0 +1,19 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+/*
+
+DO NOT DELETE THIS FILE
+=======================
+
+The purpose of this file is to allow `main-dynamic.ts` to be tsc-compiled
+BEFORE it is copied over to each of the associated example directories
+within `dist/examples`.
+
+ */
+export class AppModule {};