Bump postcss, stylelint, stylelint-config-standard, stylelint-csstree-validator and stylelint-scss

Bumps [postcss](https://github.com/postcss/postcss) to 8.4.31 and updates ancestor dependencies [postcss](https://github.com/postcss/postcss), [stylelint](https://github.com/stylelint/stylelint), [stylelint-config-standard](https://github.com/stylelint/stylelint-config-standard), [stylelint-csstree-validator](https://github.com/csstree/stylelint-validator) and [stylelint-scss](https://github.com/stylelint-scss/stylelint-scss). These dependencies need to be updated together.


Updates `postcss` from 8.4.25 to 8.4.31
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.25...8.4.31)

Updates `stylelint` from 13.13.1 to 15.10.3
- [Release notes](https://github.com/stylelint/stylelint/releases)
- [Changelog](https://github.com/stylelint/stylelint/blob/main/CHANGELOG.md)
- [Commits](stylelint/stylelint@13.13.1...15.10.3)

Updates `stylelint-config-standard` from 21.0.0 to 34.0.0
- [Release notes](https://github.com/stylelint/stylelint-config-standard/releases)
- [Changelog](https://github.com/stylelint/stylelint-config-standard/blob/main/CHANGELOG.md)
- [Commits](stylelint/stylelint-config-standard@21.0.0...34.0.0)

Updates `stylelint-csstree-validator` from 1.9.0 to 3.0.0
- [Release notes](https://github.com/csstree/stylelint-validator/releases)
- [Changelog](https://github.com/csstree/stylelint-validator/blob/master/CHANGELOG.md)
- [Commits](csstree/stylelint-validator@v1.9.0...v3.0.0)

Updates `stylelint-scss` from 3.21.0 to 5.2.1
- [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...v5.2.1)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: stylelint
  dependency-type: direct:development
- dependency-name: stylelint-config-standard
  dependency-type: direct:development
- dependency-name: stylelint-csstree-validator
  dependency-type: direct:development
- dependency-name: stylelint-scss
  dependency-type: direct:development
...

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

Author: dependabot[bot]