Missing CITATION.cff file for repository

[mhucka]

It would be useful for visitors & researchers if this repository had a CITATION.cff file, so that we can know how to properly cite it. Would you mind adding one, please?

In case it's useful, there is a handy online CITATION.cff file creation tool here: https://citation-file-format.github.io/cff-initializer-javascript/#/

For further motivation: the Zotero browser plugin knows how to read CITATION.cff files in GitHub repositories, making it easy for Zotero users to add an entry for the repository to their Zotero bibliography database and thus more likely that they will cite it in their work.

(I'm aware that the README.md file has citation info, but it's for the software, not for the repository.)

[dhkim0225]

@dev-strender What do you think about adding CITATION.cff file?