Standardised module loading system & fixed build system

Fixed broken build system in broken webpack version.
Also updates module system to standardise on ES6 import/exports,
Especially since babel has changed it's 'default' logic for the old
module system.

resources/assets/js/services/drawio.js

@@ -66,4 +66,4 @@ function drawPostMessage(data) {
     iFrame.contentWindow.postMessage(JSON.stringify(data), '*');
 }
 
-module.exports = {show, close};
+export default {show, close};