Clear and concise description of the problem

When buliding a lib, css will be extracted in a single file style.css, is there a way to bundle css in output js.

Suggested solution

Like rollup-plugin-postcss can set extract

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.