build(deps-dev): bump postcss from 8.5.6 to 8.5.8

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.6 to 8.5.8.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.6...8.5.8)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.8
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

packages/browser-ext/package.json

@@ -85,7 +85,7 @@
     "@types/react-syntax-highlighter": "^15.5.13",
     "@vitejs/plugin-react": "^5.1.1",
     "jsdom": "^29.0.1",
-    "postcss": "8.5.6",
+    "postcss": "8.5.8",
     "postcss-modules": "^6.0.1",
     "tailwindcss-cli": "^0.1.2",
     "vite": "^7.3.1",