How to reference mir (and lubeck) libraries

[jmh530]

Question from the forums:
https://forum.dlang.org/post/itbkwcpwpiemcnylgrdy@forum.dlang.org

Might be good to add answer to Readme.md.

[jmh530]

@9il ping

[bachmeil]

You only need to add a CITATION.cff as described here: https://academia.stackexchange.com/a/172780