Clear and concise description of the problem

Rsbuild has released version 1.0, and although PostCSS can be used to use Unocss, I think it is similar to Vite. It may be more convenient to create a plugin.

Suggested solution

Develop a plugin

Alternative

Configure PostCSS

Additional context

No response

Validations

• Read the Contributing Guidelines.
• Read the README.md of using the package.
• Already used the Interactive Docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.