asdf plugin for Kargo

[MPV]

Checklist

• I've searched the issue queue to verify this is not a duplicate feature request.
• I've pasted the output of kargo version, if applicable.
• I've pasted logs, if applicable.

Proposed Feature

Ship a small asdf plugin for (installing) Kargo.

Motivation

As an alternative to:

• Publish the kargo package to brew #2514
• feat: Publish kargo to brew #3011

...but using asdf, which (amongst many other things) supports declarative versioning of tools, i.e. having this in your repo or computer's .tool-versions file:

kargo 1.2.2

Suggested Implementation

Follow the asdf guide for creating a plugin, naming it asdf-kargo, merely pointing it to Kargo's GitHub repository, then publishing the repo.

In theory this could be done by any individual, but having it published by the Akuity org would grant it more trustworthiness.