build(deps-dev): bump postcss from 8.4.20 to 8.4.31 (#31)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.20 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@8.4.20...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
...

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package.json

@@ -44,7 +44,7 @@
 		"imagemin-pngquant": "^9.0.2",
 		"imagemin-svgo": "^10.0.1",
 		"mini-css-extract-plugin": "^2.7.2",
-		"postcss": "^8.4.20",
+		"postcss": "^8.4.31",
 		"postcss-loader": "^7.0.1",
 		"postcss-nested": "^6.0.0",
 		"postcss-simple-vars": "^7.0.1",