DOC: Build documentation pages

[tangkong]

Current Behavior

We have a job that publishes docs to the gh-pages branch but nothing there

Expected Behavior

We should have actual documentation

Context / environment

I remembered that his exists, set up gh to look at the branch, and now it exists but is empty 😢

Steps to Reproduce (for bugs)

N/A

Suggested Solution

Write documentation. Probably should include

• A concise explanation of our data model (which might be unintuitive to some)
• API documentation (autogenerated)
• (eventually) GUI walkthroughs