Bump postcss, react-scripts-ts and rollup-plugin-postcss

Bumps [postcss](https://github.com/postcss/postcss) to 8.4.31 and updates ancestor dependencies [postcss](https://github.com/postcss/postcss), [react-scripts-ts](https://github.com/wmonk/create-react-app) and [rollup-plugin-postcss](https://github.com/egoist/rollup-plugin-postcss). These dependencies need to be updated together.


Updates `postcss` from 5.2.18 to 8.4.31
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/commits/8.4.31)

Updates `react-scripts-ts` from 2.17.0 to 4.0.8
- [Changelog](https://github.com/wmonk/create-react-app/blob/next/CHANGELOG.md)
- [Commits](https://github.com/wmonk/create-react-app/commits)

Updates `rollup-plugin-postcss` from 1.6.3 to 4.0.2
- [Release notes](https://github.com/egoist/rollup-plugin-postcss/releases)
- [Changelog](https://github.com/egoist/rollup-plugin-postcss/blob/master/CHANGELOG-OLD.md)
- [Commits](egoist/rollup-plugin-postcss@v1.6.3...v4.0.2)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: react-scripts-ts
  dependency-type: direct:development
- dependency-name: rollup-plugin-postcss
  dependency-type: direct:development
...

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