build(deps): bump css-what from 5.0.0 to 5.1.0 in /docs

Bumps [css-what](https://github.com/fb55/css-what) from 5.0.0 to 5.1.0.
- [Release notes](https://github.com/fb55/css-what/releases)
- [Commits](fb55/css-what@v5.0.0...v5.1.0)

---
updated-dependencies:
- dependency-name: css-what
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>