Convert to use a ProcessDialog with radio buttons

This funnels all the API requests through the OOUI Process system, which handles the errors, and also has a loading state.

User scripts can't use require() to load arbitrary other script files, so we have to use Babel to compile to ES5 in order to test locally.

In production, we should be able to use ES6 as it is written here. For this reason the dist/ directory is added to .gitignore

The 'Create new item' functionality has been removed, but will be re-added once we show a notification with mw.notify, and invoke the script after it is clicked.

Also changed the key names on the translation page to have the 'asl-' prefix, so we don't need to do that in the code.