refactor: add license header to JS files & format files (#12081)

modules/@angular/platform-browser/rollup-testing.config.js

@@ -1,3 +1,10 @@
+/**
+ * @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 default {
   entry: '../../../dist/packages-dist/platform-browser/testing/index.js',
@@ -9,4 +16,4 @@ export default {
     '@angular/common': 'ng.common',
     '@angular/platform-browser': 'ng.platformBrowser'
   }
-}
+};