chore(deps-dev): bump eslint from 5.16.0 to 6.6.0 in /frontend

Bumps [eslint](https://github.com/eslint/eslint) from 5.16.0 to 6.6.0.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Changelog](https://github.com/eslint/eslint/blob/master/CHANGELOG.md)
- [Commits](eslint/eslint@v5.16.0...v6.6.0)

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