Replace zenodo.json with CITATION.cff
As we also mirror our repo to github and github provides a simple interface for directly getting the citation info on the repo sidebar.
This file format is also supported from zenodo and a similar feature might be also implemented in gitlab (https://gitlab.com/gitlab-org/gitlab/-/issues/337368). Hence we may should switch the format, to also use CFF files (https://citation-file-format.github.io/)