Bump postcss from 8.4.24 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.24 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@8.4.24...8.4.31)

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

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

package.json

@@ -32,7 +32,7 @@
     "eslint-config-prettier": "^8.5.0",
     "eslint-plugin-svelte": "^2.30.0",
     "mousetrap": "^1.6.5",
-    "postcss": "^8.4.24",
+    "postcss": "^8.4.31",
     "prettier": "^2.8.0",
     "prettier-plugin-svelte": "^2.10.1",
     "reconnecting-websocket": "^4.4.0",