Add support gRPC as in jetbrains HTTP client

[micronull]

https://www.jetbrains.com/help/idea/http-client-in-product-code-editor.html#grpc-requests

The http client jb supports grpc requests. I wish hurl would support them too.

[fabricereix]

Hi @micronull
That will be indeed good to support it. Unfortunately, this is it not something in our priority now.