Add proper citation via Zenodo archive and update CITATION.cff

[ivastar]

Hi WebbPSF team,

Thanks for all your work on this project—WebbPSF continues to be used and cited in the community even though it’s now deprecated. I'm currently editing a paper for JOSS and landed here while looking for the correct citation.

To support reproducible science and ensure that both the original authors and later contributors receive appropriate credit, I’d like to suggest two things:

1. Archive the latest release on Zenodo. This will generate a DOI that can be cited, and Zenodo will automatically include all contributors based on the GitHub commit history (assuming ORCID integration is used).

2. Update the CITATION.cff file to reference the Zenodo DOI and, optionally, also include the 2012 or 2014 SPIE papers which ASCL seems to suggest are the best citations.

Having both citations gives users a clear and citable record of both the software and its foundational publication.

An alternative option would be to edit the CITATION.cff file to reference the ASCL entry for WebbPSF. That has at least a bibcode and is indexed by ADS: 2015ascl.soft04007P however this option does not give credit to more recent contributors to the project.