Bump css-what and svgo

Bumps [css-what](https://github.com/fb55/css-what) and [svgo](https://github.com/svg/svgo). These dependencies needed to be updated together.

Updates `css-what` from 4.0.0 to 6.1.0
- [Release notes](https://github.com/fb55/css-what/releases)
- [Commits](fb55/css-what@v4.0.0...v6.1.0)

Updates `svgo` from 2.3.0 to 2.8.0
- [Release notes](https://github.com/svg/svgo/releases)
- [Changelog](https://github.com/svg/svgo/blob/main/CHANGELOG-old.md)
- [Commits](svg/svgo@v2.3.0...v2.8.0)

---
updated-dependencies:
- dependency-name: css-what
  dependency-type: indirect
- dependency-name: svgo
  dependency-type: indirect
...

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