fix(rsc): add ?direct to get actual CSS content in dev mode instead of JS module

[schiller-manuel]

No description provided.

[hi-ogawa]

I went deep dive into ?direct mechanism in #1050 and I don't think this would matter for rsc plugin. As somewhat expected, css virtual module isn't working currently but there's no way around even if we incorporate ?direct as far as I can tell (or we would need a bit more trickery or fix on Vite core side). I will explore a bit more, but will probably close this PR later.

[hi-ogawa]

#1050 is merged, so closing.