Add fetch polyfill

package.json

@@ -86,6 +86,7 @@
   "dependencies": {
     "drag-drop": "2.11.0",
     "tus-js-client": "1.1.3",
+    "whatwg-fetch": "^1.0.0",
     "yo-yo": "1.1.1"
   }
 }

src/plugins/GoogleDrive.js

@@ -1,6 +1,7 @@
-import yo from 'yo-yo'
 import Utils from '../core/Utils'
 import Plugin from './Plugin'
+import 'whatwg-fetch'
+import yo from 'yo-yo'
 
 export default class Google extends Plugin {
   constructor (core, opts) {