Bump @webref/css from 8.0.1 to 8.1.0

Bumps [@webref/css](https://github.com/w3c/webref) from 8.0.1 to 8.1.0.
- [Commits](https://github.com/w3c/webref/compare/@webref/css@8.0.1...@webref/css@8.1.0)

---
updated-dependencies:
- dependency-name: "@webref/css"
  dependency-version: 8.1.0
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]