Tailwindcss v4 integration support

[xsjcTony]

Summary

Support Tailwindcss v4 for @astrojs/tailwind integration

Background & Motivation

Tailwind has finally released v4 stable. Although it hasn't been announced via a blog post yet, but it is released.
https://www.npmjs.com/package/tailwindcss/v/4.0.0

Goals

• Support new features in v4
• Backward compatibility with v3 (or lower?)

[florian-lefebvre]

I'll be working on this, I'm waiting for the stable v4 docs

[xsjcTony]

Thanks. It's just been released: https://tailwindcss.com/

[florian-lefebvre]

withastro/astro#13049