chore(deps-dev): bump postcss from 8.4.19 to 8.4.31 (#282)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.19 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@8.4.19...8.4.31)

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

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package.json

@@ -18,7 +18,7 @@
     "glob": "^8.0.3",
     "minimist": "^1.2.5",
     "nyc": "^15.1.0",
-    "postcss": "^8.0.0",
+    "postcss": "^8.4.31",
     "semver": "^7.3.2",
     "typescript": "^4.0.3"
   },