Add CI

Add a CI to the project. It's probably better to use pixi at least for the unittest as it is now used also in diracx and lhcbdiracx projects. In diracx no conda environment is used anymore (only pixi). Check:

https://github.com/DIRACGrid/diracx/blob/v0.0.1a46/.github/workflows/main.yml

and:

https://gitlab.cern.ch/lhcb-dirac/lhcbdiracx/-/blob/master/.gitlab-ci.yml?ref_type=heads

Also check CTADIRAC project for reference.