Using GitHub citation feature

[felixschurk]

https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-citation-files

I just run across this documentation and think that could also be applicable to this repository. Would improve the metadata and also when this repository is mined the data would then be present.

One example where it is used can be seen here https://github.com/ropensci/cffr.