[FEATURE] Add developer guide for expanding protobuf support #180
Description
Is your feature request related to a problem?
As protobuf hopes to gain traction with outside contributors it may be useful to have some documentation detailing the process of expanding API support in core. Since this repo is likely the first contact for most parties interested in gRPC/proto it might be a good place to add this documentation (even though code changes are almost entirely in core).
What solution would you like?
A small document outlining the basic steps for providing support for maybe a query type with an examples of how this has been done previously.
What alternatives have you considered?
This may be better suited for the core repo. A readme could be added in the top level DEVELOPER_GUIDE.md or maybe the gRPC module README.md.
Do you have any additional context?
I think it makes sense to link to this documentation in the meta issue here which will be provided in the documentation website.