Add citation-style to cite a work in CITATION.cff

[B3J4y]

I'd like a feature that allows projects to be cited in Citation.cff as easily as with BibTeX or APA style. Currently, people has to manually inspect the .cff file and copy relevant fields, a process prone to errors.

I'm aware of Issue #64, but I believe this citation requirement differs because it's not part of CSL. Perhaps it should be, though.