Tailwind 4 (in progress)

[bep]

https://tailwindcss.com/blog/tailwindcss-v4-alpha

This seems to work on the fundamental level.

Some notes:

• Tailwind now comes with @import suppport built in, which isn't compatible with Hugo's inlineImports=true option. We probably need to establish some kind of namespace in Hugo to get both to work well together.
• This seem to work fine with PostCSS, but since the autoprefixer now is built into TailwindCSS, this could probably be much more performant if we created a resources.TailwindCSS func that uses the Tailwind Oxide directly ... Maybe.

[bep]

I will add a css.TailwindCSS template func to Hugo v0.128.0. Will be out in a day or two. It works very well with TailwindCSS v4 alpha 16.

gohugoio/hugo#12619