Bump postcss and react-scripts in /frontend

Bumps [postcss](https://github.com/postcss/postcss) to 8.4.31 and updates ancestor dependency [react-scripts](https://github.com/facebook/create-react-app/tree/HEAD/packages/react-scripts). These dependencies need to be updated together.


Updates `postcss` from 7.0.21 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/7.0.21...8.4.31)

Updates `react-scripts` from 4.0.3 to 5.0.1
- [Release notes](https://github.com/facebook/create-react-app/releases)
- [Changelog](https://github.com/facebook/create-react-app/blob/main/CHANGELOG-4.x.md)
- [Commits](https://github.com/facebook/create-react-app/commits/react-scripts@5.0.1/packages/react-scripts)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
- dependency-name: react-scripts
  dependency-type: direct:production
...

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

frontend/package.json

@@ -9,7 +9,7 @@
     "react": "^17.0.2",
     "react-dom": "^17.0.2",
     "react-json-view": "^1.21.3",
-    "react-scripts": "4.0.3",
+    "react-scripts": "5.0.1",
     "web-vitals": "^1.0.1"
   },
   "proxy": "http://localhost:8080",