Add citation information

[kequach]

I am using this client in my master thesis and would like to properly give credit to the authors/maintainers of this repo. Have you thought about adding a CFF file or codemeta file? About CFF: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-citation-files About codemeta: https://github.com/codemeta/codemeta