Bump postcss from 8.3.7 to 8.3.8

Bumps [postcss](https://github.com/postcss/postcss) from 8.3.7 to 8.3.8.
- [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/8.3.7...8.3.8)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

package.json

@@ -63,7 +63,7 @@
   "lint-staged": "^11.1.2",
   "mini-css-extract-plugin": "^2.3.0",
   "npm-run-all": "^4.1.5",
-  "postcss": "^8.3.7",
+  "postcss": "^8.3.8",
   "postcss-loader": "^6.1.1",
   "prettier": "^2.4.1",
   "release-it": "^14.11.6",