Responsive Layout and Navbar from `archlinux-common-style`

[maltejur]

This pull request is #255 rebased and with the navbar replaced by the one from archlinux-common-style via a git submodule. Currently that still links to my branch but once the pull request is closed, I will update it

I am not sure about the margin on the left and right side of the desktop version. Should it stay like it is right now, should it be removed just from the navbar, or should it be completely removed? I would keep it like it is right now.

Closes #322 #255 #212