add a gRPC example

[liamwh]

I'd love an example that has a frontend NodeJS server (like Next.JS or ideally SvelteKit) that communicates to the Rust backend using gRPC so that types for both the frontend and backend can be generated from using a protobuf

[geoffreygarrett]

+1

[jonaro00]

Once HTTP/2 is fully supported (shuttle-hq/shuttle#1582), we should definitely add gRPC examples.