feat: add hyphen subcommand to git and cd spec

[cstrnt]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
New Spec

What is the current behavior? (You can also link to an open issue here)
The - subcommand for git checkoutand cd is not implemented

What is the new behavior (if this is a feature change)?
It implements the subcommand for both specs

Additional info:

[brendanfalk]

Hey Tim - so the - is an argument not a subcommand.

So for both cd and git checkout, we will need to add the following to the arg object:

args: {
    ...,
    suggestions: [{name: "-", description: "switch to the last used folder" }]
}

I believe the prop name is suggestions however it could also be additionalSuggestions. You'll have to test

Slides 5 and 6 of this hack-night deck give you a good summary of how it works: https://docs.google.com/presentation/d/1B69F5mg0YPu7z6Y6VQkNgdWgPXCg8fVVHWcgu4BYEL4/edit#slide=id.gc60f6c760e_0_15

[cstrnt]

I totally messed that one up (and it actually works this way as well). Will change that and keep the actual way in mind

[brendanfalk]

Looks good! Here is something I just wrote up about the difference between subcommands, options, and arguments. Definitely needs a look over, but high level stuff is there: https://forum.withfig.com/t/cli-tools-the-difference-between-a-command-subcommand-option-and-argument/56