Listing older versions of the API docs

[savetheclocktower]

Right now, the page at docs/api/pulsar.md includes a template linking to the most recent Pulsar release.

We should figure out how to expand this to include links to previous versions so that this page can be more useful — right now it's just sort of a speed bump. Creating an issue so that I remember to do this.

[confused-Techie]

This is one I'd actually be fairly confident to resolve as well if you'd like. Once we get the re-orginization merged I can tackle it