feat: yadm integration with selected gh subcommands

[pgierz]

It would be great if yadm could do something like this:

$ yadm issue list
# In the background, calls:
# gh issue -R pgierz/dots list

At the moment, this is implemented in the config of yadm's gitconfig:

[alias]
  issue = "!f() { gh issue -R pgierz/dots \"$@\"; }; f"
  pr = "!f() { gh pr -R pgierz/dots \"$@\"; }; f"

Ideally, I'd like to be able to do this from any git, so it should eventually
be integrated somehow into ~/.config/git/config. The corresponding scripts
should be in ~/.local/sbin/ or similar.

One idea would be to version control the script for this, and then bootstrap it
into yadm's gitconfig.