Add basic install / uninstall and library loading test

Ok, I am unsure what the problem here is, this test already failed with the same error message, BEFORE the implementations from 📌 Fix the remaining compatibility issues Fixed were implemented. I just pushed 📌 Fix the remaining compatibility issues Fixed to dev, since I thought, the changes there would fix the problem here.

I guess it's because the library isn't loaded or even downloaded into the libraries folder. I guess we need the CDN snippet if library isn't present locally... Mhm... hope this doesn't grow toooooo large!

OK, let's set this issue postponed for now, we can work on the cdn implementation when there is time for it.

POSTPONED on 📌 Create an option to alternatively load the js library via cdn Active .