[pgAdmin4][patch][RM#2593]: Query Tool/ Debugger won't load withQt-5.1 with webkit

Hi

When an instance of query tool and debugger is opened, it fails to load and gives following error in console:

`Promise is undefined.`

The reason is: These instances are loaded in an iframe and their bundles don't include `babel-polyfill` library. Babel-polyfill must be loaded first.

Please find attached patch and review it. Thanks to Khushboo for reporting it.

Thanks,

Surinder