Consider adding a CITATION.cff file

Description

Congratulations on having TRExFitter finally become globally public code and getting its Zenodo DOI! 🎉 That's very exciting. 😀

To make things easier to cite and to also have an easier to maintain file than the existing .zenodo.json, consider adopting the CITATION.cff file standard. It has broader support and also multiple citation tools know how to interact with it.

If you have questions or need examples feel free to ping me.