feat(esnext): use babel polyfill to enable async/await syntax for esnext projects

closes #959

Author: 3cp

lib/commands/new/buildsystems/cli/index.js

@@ -62,7 +62,8 @@ module.exports = function(project, options) {
           {
             'path': 'node_modules/aurelia-cli/lib/resources/scripts/configure-bluebird.js',
             'env': 'dev'
-          }
+          },
+          'node_modules/@babel/polyfill/browser.js'
         ],
         dependencies: [
           // only needs packages not explicitly depend

lib/resources/src/main-webpack.js

@@ -1,3 +1,4 @@
+import '@babel/polyfill';
 import environment from './environment';
 import {PLATFORM} from 'aurelia-pal';
 import * as Bluebird from 'bluebird';