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
- Upgrade stylelint and plugin
- Change ruleset to a explicit one, with all deprecated rules removed
- Fix new issues detected by value validation
For `overflow: overlay` see
https://github.com/stylelint/stylelint/issues/6667
Previous solution that re-purposed the 'hide' class by making it
`!important` had various unintended side-effects where jQuery .show() was
not able to outweight it. Use a separate class to prevent these
interactions.
By appending the tooltips to `document.body`, we can avoid any stacking context issues caused by surrounding element's CSS.
This uses [tippy.js](https://github.com/atomiks/tippyjs) instead of Fomantic popups. We should aim to replace all Fomantic popups with this eventually and then get rid of the Fomantic `popup` module completely.
