Add CITATION.cff

[schackartk]

Is your feature request related to a problem? Please describe.
I am unsure of how to properly cite coveragepy in a research article.

Describe the solution you'd like
I would like to see a CITATION.cff file in the root of the repository.

GitHub recommends, and integrates support for, CITATION.cff files. Inclusion of this file would immediately have these benefits:

• Users will have the necessary metadata to properly cite mypy.
• GitHub can automatically generate both APA and BibTeX formatted citations. A "Cite this repository" option will automatically appear on the repo's sidebar when viewed on a desktop browser.
• Reference managers like Zotero will automatically detect the metadata so the user can save the citation to their library.

Describe alternatives you've considered
The other main options are to supply a suggested citation in the README or other documentation, or to have a BibTeX formatted citation file. However, GitHub has better support for CFF formatted citations.

Additional context
Examples of popular packages using this are pandas and tensorflow.

I would be happy to create an initial version of this and open a PR if there is interest in possibly merging it after refinement.

[nedbat]

I'm fine with adding this file. It would be nice if it didn't need to be a separate file, but I understand.

[schackartk]

Yeah, it can always be a pain adding yet another file to the root of the repo.

I will draft one up and submit a pull request though.