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 8th of May from 18:00 to 20:00 we will be performing maintenance on GitLab. During this time the service will be unavailable, apologies for any inconvenience.