Bump postcss and css-loader

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


Updates `postcss` from 7.0.39 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@7.0.39...8.4.31)

Updates `css-loader` from 3.5.3 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](webpack-contrib/css-loader@v3.5.3...v6.8.1)

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

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

package.json

@@ -103,7 +103,7 @@
     "chai-datetime": "^1.6.0",
     "concurrently": "^5.2.0",
     "core-js": "^3.6.5",
-    "css-loader": "^3.5.3",
+    "css-loader": "^6.8.1",
     "cypress": "^5.1.0",
     "eslint": "^7.32.0",
     "eslint-config-prettier": "^8.3.0",