build(aio): refactor dgeni packages

This is to tidy up the `author-packagse`, which currently duplicates a
lot of the configuration in the main packages. We need to
DRY this up so that we don't fall foul of a change in one being missed in
the other.

aio/tools/transforms/angular-api-package/mocks/importedSrc.ts

@@ -0,0 +1,9 @@
+/**
+ * @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
+ */
+
+export const x = 100;

aio/tools/transforms/angular-api-package/mocks/testSrc.ts

@@ -0,0 +1,42 @@
+/**
+ * @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
+ */
+
+/**
+ * @module
+ * @description
+ * This is the module description
+ */
+
+export * from './importedSrc';
+
+/**
+ * This is some random other comment
+ */
+
+/**
+ * This is MyClass
+ */
+export class MyClass {
+  message: String;
+
+  /**
+   * Create a new MyClass
+   * @param {String} name The name to say hello to
+   */
+  constructor(name) { this.message = 'hello ' + name; }
+
+  /**
+   * Return a greeting message
+   */
+  greet() { return this.message; }
+}
+
+/**
+ * An exported function
+ */
+export const myFn = (val: number) => val * 2;