Architecture/Exposing a library crate

[rubberduck203]

We've had some conversation of how it would be nice to reuse parts of scope as a library.
Particularly, the analyze/fix functionality would be a high value item to extract into a crate that could be published and imported into other rust programs.

In it's current state, there really is no intentional public API and a fair amount of the cli is mixed into various modules (both as feature/cli.rs modules and peppered throughout the code).

This document attempts to capture the current state, identify things that may cause problems for us when attempting to solidify & publish a public API, and establish a potential path forward/goal state.

I'm not sure if we want to merge it or not, but a PR does provide a convenient way to leave comments/thoughts.

I obviously used an LLM to assist me in creating the document, but I reviewed and edited it myself. It's pretty accurate and the approach it lays out for refactoring is pretty solid IMO.

[kejadlen]

I think this is a reasonable approach if we do want to reuse some of the functionality, although perhaps might make more sense in a GitHub issue for now?