Add tests, docs, build

[TNick]

This is just a preview to get the discution started.

I has to upgrade ol and ol-ext to be able to run jest.

[manisandro]

If I may add one remark right away, I'm a bit skeptical about comments just for the sake of writing a comment but which don't add any real information. In my view they just make the code more cluttered and ultimately less readable.

[TNick]

Thanks for the feed-back. Do you have specific examples?

Most of the commetns are written so that they show up in the documentation. I'm in the habbit of interseeding comments before every few lines of code because I find it easier to understand said code a few month after. Especially so with JS. Python is easier on the eyes. My personal experience with open source projects is that the contributors are more likely to contribute if the code is well commented.

That being said I admit that the main reason for writing the comments in code was to give me time to absorb the concepts and to form a mental map of the code.

[manisandro]

For instance this comment does not really add any meaningful information further than what is already clear from the code:

[TNick]

Is this the intendend behaviour? Only show the notification if the visibility of a different layer is set.

See the test here:
https://github.com/AdvaitaTopCad/qwc2/blob/8a49f2839ee67107be99a90fbf47d5c83adaaf91/utils/ThemeUtils.test.js#L243