Add OpenRPC support to define plugin API

[shanejonas]

Xi-Editor Issue Template

• I have searched existing issues and could not find my issue.
• I have studied the documentation.

Details

I think this project could benefit from integration with OpenRPC which provides a base foundation for service discovery and tooling such as documentation/client generation/mock server for JSON-RPC akin to OpenAPI/Swagger.

Here is an example of the OpenRPC playground, it gets the OpenRPC Document via calling the rpc.discover method:

https://playground.open-rpc.org/?url=https://mock.open-rpc.org/petstore-1.0.0

and just the bare inspector:
https://inspector.open-rpc.org/?url=https://mock.open-rpc.org/petstore-1.0.0

Let me know how I can help.

[LiHRaM]

I think this is a really good idea. Do you have an idea for how this could be implemented for Xi? Got any specific crates in mind, maybe?