fish: support simple key bindings

[arulagrawal]

In fish shell, support simple keybinds of the form "SEQUENCE" -> COMMAND, as described in the fish docs: https://fishshell.com/docs/current/cmds/bind.html

Description

Support generating simple keybinds for fish shell. The implementation is the same as that for the aliases which existed already, however I am unsure of the escapeShellArg function. It's presence would break the 3rd test case (I included this specifically because it is listed as an example in the docs, but maybe there is a better way to handle this?

Edit: Not sure what mistake I made earlier but I'm pretty sure it works (tests passing).

This is my first time contributing to nix stuff so any pointers are appreciated.

Checklist

• Change is backwards compatible.

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[arulagrawal]

I guess this may run afoul of the "Add only valuable options" guideline, and seeing as no one added this small option already, I don't disagree since these simple binds could easily be placed in interactiveShellInit.

@rycee (wasn't sure who else to ping)

[stale]

Thank you for your contribution! I marked this pull request as stale due to inactivity. Please read the relevant sections below before commenting.

If you are the original author of the PR

• GitHub sometimes doesn't notify people who commented / reviewed a PR previously when you (force) push commits. If you have addressed the reviews you can officially ask for a review from those who commented to you or anyone else.
• If it is unfinished but you plan to finish it, please mark it as a draft.
• If you don't expect to work on it any time soon, please consider closing it with a short comment encouraging someone else to pick up your work.
• To get things rolling again, rebase the PR against the target branch and address valid comments.

If you are not the original author of the PR

• If you want to pick up the work on this PR, please create a new PR and indicate that it supercedes and closes this PR.