Bump yaml, cssnano and postcss-load-config

Bumps [yaml](https://github.com/eemeli/yaml) to 2.2.2 and updates ancestor dependencies [yaml](https://github.com/eemeli/yaml), [cssnano](https://github.com/cssnano/cssnano) and [postcss-load-config](https://github.com/postcss/postcss-load-config). These dependencies need to be updated together.


Updates `yaml` from 1.10.2 to 2.2.2
- [Release notes](https://github.com/eemeli/yaml/releases)
- [Commits](eemeli/yaml@v1.10.2...v2.2.2)

Updates `cssnano` from 5.1.0 to 6.0.0
- [Release notes](https://github.com/cssnano/cssnano/releases)
- [Commits](https://github.com/cssnano/cssnano/compare/cssnano@5.1.0...cssnano@6.0.0)

Updates `postcss-load-config` from 3.1.3 to 4.0.1
- [Release notes](https://github.com/postcss/postcss-load-config/releases)
- [Changelog](https://github.com/postcss/postcss-load-config/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss-load-config@3.1.3...v4.0.1)

---
updated-dependencies:
- dependency-name: yaml
  dependency-type: indirect
- dependency-name: cssnano
  dependency-type: direct:development
- dependency-name: postcss-load-config
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]