@nicolas search for theme exodus.its persona fork with widgets, it not finished but it can help you to see the code
SOLVED JQuery in Widget Template
Use Case - Wanting to use JQuery datepicker in my widget for some reason it wasn't working
NodeBB Version - "1.1.2"'
You should be able to just use the globally provided jQuery object.
You can close this thread..
Resolved by using app.loadJQueryUI()