Switch the JavaScript from jQuery to vanilla JS

[oliverklee]

The Bootstrap package has not been providing jQuery out of the box anymore for quite some time, and JavaScript in modern browsers has evolved so that things are now possible without a big hassle that required usage of jQuery a few years back.

So I propose dropping the implicit jQuery dependency and reworking the JavaScript from using jQuery to vanilla JS.

This will also allow sites that use femanager to drop jQuery, which reduces page load times.

https://tobiasahlin.com/blog/move-from-jquery-to-vanilla-javascript/
https://dev.to/rfornal/-replacing-jquery-with-vanilla-javascript-1k2g