build(deps-dev): bump postcss-cli from 11.0.1 to 12.0.0 in /docs (#7364)

Bumps [postcss-cli](https://github.com/postcss/postcss-cli) from 11.0.1 to 12.0.0.
- [Release notes](https://github.com/postcss/postcss-cli/releases)
- [Changelog](https://github.com/postcss/postcss-cli/blob/master/CHANGELOG.md)
- [Commits](postcss/postcss-cli@11.0.1...12.0.0)

---
updated-dependencies:
- dependency-name: postcss-cli
  dependency-version: 12.0.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Author: dependabot[bot]