Fish completions

[arcuru]

Opening this as a PR, and removing the link to the fish shell completions gist (the link was broken anyways after I renamed my account). If you don't want the completions merged, I can remove the completions script and just update the docs for the correct link.

The fish shell completions now respect SD_ROOT and should work fine. I've used this daily since I wrote it 1.5 years ago, and have never needed to fix anything. Note that this also works for completing the special commands cat edit help new which, which the zsh completions don't handle.

I will update home-manager, and the docs for that, myself if you want to merge this.

[ianthehenry]

Hey neat! Yeah, it looks great. Could you update the readme with instructions on how to install the completions? (Maybe this is just known for fish users and not necessary?)

[arcuru]

Sorry for the delay, been a bit busy lately.

Updated the docs with a description of how to manually install. I will loop back around and update the nix instructions if needed once this is packaged.