Add API reference links in navbar dropdown

[kid-icarus]

This adds a dropdown to the navbar with a couple of links for the API reference for JS and Rust versions of Automerge. I can add more, but just wanted to see folks agree with the direction first.

Screen.Recording.2024-03-02.at.12.45.50.PM.mov

[pvh]

This is a good start! Do we have appropriate Swift docs as well, @heckj?

[pvh]

Glanced at the code -- we probably ought to set things up so we don't have a hardcoded point release in the rust link as well. That can really come back to bite you with Google search results as well. Any thoughts, @alexjg?

[heckj]

definitely: https://automerge.org/automerge-swift/documentation/automerge/

And I'd recommend using the link https://docs.rs/automerge/latest/automerge/ for the Rust docs so that the docs stayed tracking the 'latest' version, rather than being pinned to 0.5.7 - we'll never remember to look for an update that on releases... (at least I wouldn't)

[kid-icarus]

Ah I didn't notice the version hard coded in the URL, updated the link and also added one for the Swift docs 👍🏻