Rename astronaut-analysis.py to astronaut_analysis.py so it can be imported properly. Improve .gitlab-ci in order to test against python 3.9 up to python 3.11. Add pytest and wrap it inside acceptance-test.sh. Fix various datetime related errors in astronaut_analysis.py. Add CITATION.cff. Update package versions in requirements.txt. Add requirements for tests and CI/CD in separate requirement files. Add VERSION.txt, so versioning of this package can be handled bettter.