fix(@angular/cli): add missing WeakMap polyfill

Author: trotyl

packages/@angular/cli/blueprints/ng/files/__path__/polyfills.ts

@@ -31,6 +31,7 @@
 // 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';
 
 /** IE10 and IE11 requires the following for NgClass support on SVG elements */