Bump postcss in /docs in the npm_and_yarn group across 1 directory (#318)

Bumps the npm_and_yarn group with 1 update in the /docs directory: [postcss](https://github.com/postcss/postcss).


Updates `postcss` from 8.5.16 to 8.5.23
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.16...8.5.23)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.23
  dependency-type: indirect
  dependency-group: npm_and_yarn
...

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Author: dependabot[bot]