Removal of all Package Files and References in favour of Firefox Color

Fixing #14 had me realise how convoluted the steps for building here are – that is without even trying to release the changes through actually compiling the .xpi files for the Firefox Addon Store. I wanna propose to just drop that way of distribution completely in favour of the also existing Firefox Color way of handling the Themes. It's easier to handle and further also allows user to customise to their liking (Oledpuccin anyone?). I think in the long run this could actually benefit everyones sanity. :D