Ran most of the Less files through the Less compiler and Prettier and
then followed up with a round of manual fixes.
The Less compiler had unfortunately stripped all `//` style comments
that I had to restore (It did preserve `/* */` comments). Other fixes
include duplicate selector removal which were revealed after the
transpilation and which weren't caught by stylelint before but now are.
Fixes: https://github.com/go-gitea/gitea/issues/15565
- Create theme at runtime which follows the CSS variables of the site
- Disable a few opinionated Monaco defaults like minimap and word highlights
- Move styles to separate file
Co-authored-by: zeripath <art27@cantab.net>