Initial idea was found on a July 27, 2021 tweet from Nat Friedman (CEO of GitHub):
We’ve just added built-in citation support to GitHub so researchers and scientists can more easily receive acknowledgments for their contributions to software.
Just push a CITATION.cff file and we’ll add a handy widget to the repo sidebar for you.
Enjoy! 🎉
The About CITATION files page on the GitHub Docs site provides formatting instructions for creating a CITATION.cff file.