馃懛 Add CI build config
- Use tox for running the tests and setting up the environment
- The TU Gitlab instance does not have any CI runners available, but it's good to have CI set up and ready to go anyway.
On the 5th of December from 18:00 to 20:00, We will be upgrading GitLab. During this time the service will be unavailable, apologies for any inconvenience.