Bump postcss from 8.4.29 to 8.4.31 in /extensions/react-widget

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.29 to 8.4.31.
- [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/8.4.29...8.4.31)

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

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

extensions/react-widget/package.json

@@ -38,7 +38,7 @@
     "@types/react-dom": "^18.0.9",
     "@vitejs/plugin-react-swc": "^3.0.0",
     "autoprefixer": "^10.4.13",
-    "postcss": "^8.4.20",
+    "postcss": "^8.4.31",
     "typescript": "^4.9.3",
     "vite": "^4.0.0",
     "vite-plugin-dts": "^1.7.1"