Easy JS alternative to this module

Problem/Motivation

This is a great module, and I have been using it for a while. I'm in the middle of upgrading a site to D11, and I needed a D11 way.

There is an easy vanilla JS way to do this:

https://github.com/codeshackio/multi-select-dropdown-js

I tested it and it works. But it lacks hierarchal grouping which this module still solves. Maybe it might be added later.

Not sure if you want to incorporate this JS library into this module (up to the maintainer to decide). I just created this issue in case others might be interested.