feat: support css module :export

[JSerFeng]

Summary

support :export in css module

close #5454

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[JSerFeng]

!canary

[github-actions]

0.6.1-canary-b0566d6-20240412151129

[xc2]

thanks @JSerFeng !

it works fine with style-loader and CssExtractRspackPlugin.

however when i extract css with experiments.css, the css output becomes wired.

Source

html {
  --foo-color: #0f0;
}

:export {
  content: "`foo`";
  color: var(--foo-color);
}

Output

html {
  --foo-color: #0f0;
}
:e

Reproduce:

https://github.com/xc2/rspack-repro-css-modules-var-export/tree/recheck

git clone https://github.com/xc2/rspack-repro-css-modules-var-export
git checkout recheck
pnpm i
pnpm build:exp-css
# then check files in dist-rspack-exp-css

[JSerFeng]

however when i extract css with experiments.css, the css output becomes wired.

Thank you, I'll fix it soon