Client-side query schema

[paralin]

You might want to fetch some data from the client, I.E. make a GET request, or store other local state like auth info.

This is still a good candidate for data managed by rGraphQL, but cannot be placed on the server.

I propose allowing users to apply a client-side schema extension which adds a schema and resolver functions for client-side data. This may be blocked until the Node API surface is finalized.