Bump postcss and css-loader

Bumps [postcss](https://github.com/postcss/postcss) to 8.4.31 and updates ancestor dependencies [postcss](https://github.com/postcss/postcss) and [css-loader](https://github.com/webpack-contrib/css-loader). These dependencies need to be updated together.


Updates `postcss` from 7.0.35 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/compare/7.0.35...8.4.31)

Updates `postcss` from 8.2.10 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/compare/7.0.35...8.4.31)

Updates `css-loader` from 1.0.0 to 6.8.1
- [Release notes](https://github.com/webpack-contrib/css-loader/releases)
- [Changelog](https://github.com/webpack-contrib/css-loader/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack-contrib/css-loader/compare/v1.0.0...v6.8.1)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: css-loader
  dependency-type: direct:development
...

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

package.json

@@ -141,7 +141,7 @@
     "buffer": "5.1.0",
     "case-sensitive-paths-webpack-plugin": "2.3.0",
     "create-file-webpack": "1.0.2",
-    "css-loader": "1.0.0",
+    "css-loader": "6.8.1",
     "enzyme": "3.11.0",
     "enzyme-adapter-react-16": "1.15.5",
     "enzyme-to-json": "3.6.1",