Bump postcss, stylelint, stylelint-order and stylelint-scss

Bumps [postcss](https://github.com/postcss/postcss) to 8.4.39 and updates ancestor dependencies [postcss](https://github.com/postcss/postcss), [stylelint](https://github.com/stylelint/stylelint), [stylelint-order](https://github.com/hudochenkov/stylelint-order) and [stylelint-scss](https://github.com/stylelint-scss/stylelint-scss). These dependencies need to be updated together.


Updates `postcss` from 7.0.39 to 8.4.39
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@7.0.39...8.4.39)

Updates `stylelint` from 13.13.1 to 16.6.1
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/main/CHANGELOG.md)
- [Commits](stylelint/stylelint@13.13.1...16.6.1)

Updates `stylelint-order` from 4.1.0 to 6.0.4
- [Release notes](https://github.com/hudochenkov/stylelint-order/releases)
- [Changelog](https://github.com/hudochenkov/stylelint-order/blob/master/CHANGELOG.md)
- [Commits](hudochenkov/stylelint-order@4.1.0...6.0.4)

Updates `stylelint-scss` from 3.21.0 to 6.4.0
- [Release notes](https://github.com/stylelint-scss/stylelint-scss/releases)
- [Changelog](https://github.com/stylelint-scss/stylelint-scss/blob/master/CHANGELOG.md)
- [Commits](stylelint-scss/stylelint-scss@3.21.0...v6.4.0)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: stylelint
  dependency-type: direct:development
- dependency-name: stylelint-order
  dependency-type: direct:development
- dependency-name: stylelint-scss
  dependency-type: direct:development
...

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