The Feature class seems like a key conceptual and organizational unit. It's used throughout the code base, but there's no documentation. Adding documentation for this particular item would be pretty high impact, IMO. It would make it much easier to use for beginners.

Here are some thoughts for an outline:

Feature Class Documentation

• Overview
  • Purpose
  • Client Feature vs Server Feature classes
• Server Feature
  • Arguments
    • schema
    • createResolversFunc
      • When is it invoked?
        • What should it return?
        • Using pubsub
          • explain the pubsub argument
      • createContextFunc
        • when is it invoked?
        • what should it return?
      • middleware
      • Hierarchical composition
        • explain new Feature(counter, post, user, graphqlTypes); in modules/index.js`
• Client Feature
  • Arguments
    • navItem
    • tabItems
    • route
    • reducer
    • features
  • Hierarchical composition
• Tutorial:
  • add a server feature
    • add a model using a migration
    • add graphql schema
    • add resolvers
  • add a client feature that uses the server feature