## Summary
This PR makes Rspack support explicit for `@tailwindcss/webpack` by
adding `@rspack/core` as an optional peer dependency alongside
`webpack`.
The loader already works through Rspack's webpack-compatible loader API,
as shown in this runnable example:
https://github.com/rstackjs/rstack-examples/tree/main/rspack/tailwindcss.
The README and package description are updated to document that usage.
## Test plan
No Rspack-specific tests were added. The loader implementation is
unchanged, and the existing webpack loader tests exercise the same
loader API path that Rspack uses, which should cover the relevant
behavior.
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Co-authored-by: Robin Malfait <malfait.robin@gmail.com>
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