Fix#33197
Improve the rendering of code blocks in markdown content
for better readability and UI stability across screen sizes.
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
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
