chore(polyfills): add comment why use es6/array

Author: rdlabo

packages/schematics/angular/application/files/src/polyfills.ts

@@ -28,12 +28,19 @@
 // import 'core-js/es6/math';
 // import 'core-js/es6/string';
 // import 'core-js/es6/date';
-import 'core-js/es6/array';
 // import 'core-js/es6/regexp';
 // import 'core-js/es6/map';
 // import 'core-js/es6/weak-map';
 // import 'core-js/es6/set';
 
+/**
+ * If your app need to indexed by Google Search, your app require polyfills 'core-js/es6/array'
+ * Google bot use ES5.
+ * FYI: Googlebot uses a renderer following the similar spec to Chrome 41.
+ * https://developers.google.com/search/docs/guides/rendering
+ **/
+import 'core-js/es6/array';
+
 /** IE10 and IE11 requires the following for NgClass support on SVG elements */
 // import 'classlist.js';  // Run `npm install --save classlist.js`.