Add CITATION.cff file

[cgobat]

PR summary

Two years ago, in a9d5a89, the repository's BibTeX citation file was moved and renamed to be compatible with GitHub's new citation format. Building upon that, this PR adds a CITATION.cff file: CFF (citation file format) files are special YAML files with native GitHub support and direct integration with the "Cite this repository" feature. CFF is capable of providing incredibly rich metadata, and isn't LaTeX- or language-specific, so CFF files can easily be exported in a variety of popular citation formats.

As an example of such a file in use, see CITATION.cff in pandas-dev/pandas (though the one added in this PR contains even more detail!).

Because the CFF definition uses jsonschema, CFF files can be easily validated (e.g. using cffconvert, or through GitHub Actions, using dieghernan/cff-validator). A workflow to do this automatically when the file is altered has also been added, in .github/workflows/cff-validator.yml.

This may or may not replace the existing CITATION.bib—some further discussion about the role of that file is warranted prior to removal.

PR checklist

• [N/A] "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested (validated using cffconvert)
• [N/A] Plotting related features are demonstrated in an example
• [N/A] New Features and API Changes are noted with a directive and release note
• [N/A] Documentation complies with general and docstring guidelines

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[tacaswell]

I am 👍🏻 on adding this file, but 👎🏻 on adding the validation workflow. This file is going to be effectively static so I do not anticipate there being a need re-validate that we have not messed the file up.

[cgobat]

Thanks @tacaswell. I will remove the cff-validator.yml file from the workflows then.

[tacaswell]

@cgobat Are you comfortable squashing this to one commit?

[cgobat]

Yep—however you want to do it is fine by me.

[tacaswell]

Can you please squash it then :)

[cgobat]

Sure, done. Wasn't sure whether you were going to do it on your side as part of the merge operation.