More GraphQL language feature examples

It would be grand to add more examples to the schema of new features we have. That way, we can fully demonstrate the features of GraphiQL, etc to newcomers!

high priority:
- fields with resolvers that yield after a delay, for demoing @defer/@stream

all else:
- unions
- interfaces implementing interfaces
- custom directives and scalars maybe? demoing new directive introspection features would be nice
- subscriptions - how to do this with netlify functions though? possible with aws in a complicated way... would be cool to have a subscription field that provides realtime starship coordinates