Feature Request: Add streaming support

[robgraeber]

The current implementation of grpc-web-ruby provides support for unary gRPC-Web calls. However, it does not yet support gRPC streaming, which is an essential feature for many real-time and high-throughput applications.

When making a streaming request that returns a enumerator this library returns 500s but it streams correctly with grpc server + envoy.

[robgraeber]

I managed to get streaming working on my fork: stimulating-ai@c9113a1

Fair warning I did it all with AI so it's dirty for sure.