Adds feathers-rpc

[jamesvillarrubia]

Summary

This lightweight middleware enables RPC style verbs on Feathers routes that then can (optionally) trigger custom methods. This allows custom-method calls when external systems cannot modify header requests and leverage x-service-method.

This problem originated from integration issues with legacy webhook software and tooling. By enabling path-only custom method triggers, there's no need to pollute the request.body with special fields.

Other Information

This has been tested with both Koa and Express in v5, and Express only in v4. Automated tests use integration tests for Koa and Express in v5 only. Will expand to v4 as necessary.