Allow modals

When prompting the user via ES's `confirm()` method, we'll get this error in Console:
```v8
Ignored call to 'confirm()'. The document is sandboxed, and the 'allow-modals' keyword is not set.
> onclick @ admin.php?page=x:200 
```

More info: https://googlechrome.github.io/samples/block-modal-dialogs-sandboxed-iframe/