set up CI via github actions

[KonradUdoHannes]

• The CI should run the pre-commit hooks and the unit tests for the bakcend.
• Unit tests for the frontend are out of scope for this issue as its currently not clear if and how they will be set up
• There should be separate workflows for frontend and backend.
• CI should run on PR to development and should allow manual workflow dispatch

[KonradUdoHannes]

Contrary to the initial formulation of the issue separate workflows for frontend and backend is questionable as pre-commit runs both the frontend and backend hooks at once as well as some general file formatting hooks (end of line fix etc.) that are common to both backend and frontend.