Implement GitHub workflow for automated front-end tests

[TFphoenix]

• Ensure Karma configuration is complete and correct
• Add some UTs, that will be automatically executed by the workflow (i.e. Karma runner)
• Implement GitHub workflow for automated tests
• Ensure the implemented workflow works properly (e.g. by using ACT)
• Optional: Integrate/Configure E2E tests (see this)

PS: This is what I consider, in my opinion, that should be done in order to automate tests on the front-end. Feel free to discuss this issue, and offer your input accordingly

Also see: https://github.com/oakestra/dashboard/issues/35