Shell completions

[VorpalBlade]

This implements issue #478 and issue #437.

Notes:

• I have not tested the fish completion myself, but simply installed it where other packages install their fish completions on Arch Linux.
• The zsh completion has changed slightly from the one in the issue, as I have learned more about how to properly write zsh completion files since then.
• The PKGBUILD is updated in this commit, but the changes will need to be synced to the AUR repo PKGBUILD to update that one as well.

[VorpalBlade]

@Askannz Hi! Any update on getting this merged?

[a-viv-a]

I appreciate you using the fish completions I wrote - fish has added Optimus completions on their end so adding those is no longer needed, they ship with fish shell.

[VorpalBlade]

@isaec I don't know how it is for fish, but zsh encourages projects to ship their own completions rather than having completions bundled with zsh, as that allows keeping things up-to-date easier, and ensures the completions matches the installed version.

I can certainly remove the fish completions from the PR, but are you sure?

[a-viv-a]

I don't know what fish recommends, sorry - just wanted to inform you.

[es20490446e]

1. Have a look if the completions provided by fish itself are sufficient.
2. Edit this pull request accordingly.
3. Reopen.

[a-viv-a]

I'll close #437 too, thanks

[VorpalBlade]

1. Have a look if the completions provided by fish itself are sufficient.
2. Edit this pull request accordingly.
3. Reopen.

@es20490446e these are zsh completions, not fish. So that doesn't make any sense to me. Why exactly did you close this PR?

EDIT: Ah, seems I included fish completions too for some reason? Strange since I don't use fish. I cannot comment on if fish completions are useful or not.

[es20490446e]

Then:

1. Remove the fish completions.
2. Reopen.

And I will merge 🫗

By the way, from now on, I will be merging any correct pull request in a couple of days max.