Is your feature request related to a problem? Please describe.

The spec is agnostic on transport, and this library provides a few different ones. The Drupal server implementation, for instance, allows for HTTP GET JSON-RPC requests in order to aid in making the responses cacheable.

Describe the solution you'd like

We should provide a transport (or option for the existing HTTP transport) to send these requests by GET instead of POST.

Describe alternatives you've considered

None obvious...

Additional context

I'm going to attempt a POC this week.