Support reference deletion

[tobia80]

Please provide support for reference deletion. With that support we can delete branches for example.
https://docs.github.com/en/rest/git/refs?apiVersion=2022-11-28#delete-a-reference

[fedefernandez]

@tobia80, it would be great indeed. I couldn't find the time to do it.

#818 and #811 are good examples of how to add new endpoints in case someone wants to contribute.