[minify-literals] Consider switching away from `clean-css`

[Erdragh]

On clean-css's repo README it states it's in maintenance mode:

IMPORTANT: clean-css is now in a clean-css/clean-css#1209. PRs are still welcome, and I will try do an occasional bugfix release.

My components extensively use Nested CSS, which is Baseline 2023. As clean-css is in maintenance mode and not accepting any new features, there will likely not be any support for it. I wanted to look into reducing my library's footprint and the only real option I found was minify-literals or rather the vite plugin using it.

I am not intimately familiar with the world of CSS minifiers, but a quick Google search nets me CSSNano, which seems to use PostCSS, which should support CSS Nesting.

[explodingcamera]

Hi, I currently don't use this package for any projects personally but I'd be happy to accept an pr. Otherwise it might take a white for me to get to it. Right now, I lean more towards not depending on postcss but it seems like that's the only option from my limited research.

Edit: seems like lightning css could work well, however the HTML minifier also seems to be unmaintained and probably also needs to be changed.

[Gaubee]

@explodingcamera I have provided more abundant support for the current css-literals and I hope to hear your opinions.
#6