Improve sidebar menus in Vector 2022
Created by: lahwaacz
The first screenshot in https://github.com/archlinux/archwiki/pull/69#pullrequestreview-1657967184 shows that the left sidebar menus in Vector 2022 look weird: the TOC menu has wrong font color and white background but no border, and the main menu above it has actually slightly different background from the rest of the page.
After these changes, the menus look like this:
This extends https://github.com/archlinux/archwiki/pull/69, I will rebase when it is merged.
/cc @nl6720 @christian-heusel