Added ruby template

[ngiger]

Tried to follow the conventions. E.g. one of the few to have a README.md, maintainers and description.

[ngiger]

Tested with nix 2.7.0

[ngiger]

I don't know why nix flake init -t github:ngiger/templates#python is working in an empty directory of mine, but not nix flake init -t github:ngiger/templates#ruby which answers with

error: cannot find flake attribute 'github:ngiger/templates#ruby

But one day after it worked without a problem. (Using nix 2.7.0)

[emptyflask]

This is good to have, but why pull in r10k (and all its dependencies) by default? If the intent is to have an example gem, maybe something like minitest?

[emptyflask]

Otherwise, I think this should be merged in to encourage ruby development on nix!

[garbas]

Just to set the expectations here. I'm planning to write up the initial rules how which templates should be added in this repository (and what they should include) and which templates should be moved to nix-community/templates. I plan to get to this task later this week or beginning of next week.

In will then also review this PR.

[supermarin]

@garbas Ping on this ^