Bump flatted and react-scripts in /frontend

Bumps [flatted](https://github.com/WebReflection/flatted) to 3.4.1 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 `flatted` from 2.0.1 to 3.4.1
- [Commits](WebReflection/flatted@v2.0.1...v3.4.1)

Updates `react-scripts` from 3.4.1 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-3.x.md)
- [Commits](https://github.com/facebook/create-react-app/commits/react-scripts@5.0.1/packages/react-scripts)

---
updated-dependencies:
- dependency-name: flatted
  dependency-version: 3.4.1
  dependency-type: indirect
- dependency-name: react-scripts
  dependency-version: 5.0.1
  dependency-type: direct:production
...

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Author: dependabot[bot]