Contribute
Fork the yap repo here and send a pull request.
For local development setup (Composer, tests, preflight, OpenAPI), see the repository CONTRIBUTE.md at the project root.
For testing Twilio call flows locally, run the yap server and then use ngrok. Grab the ngrok hostname that is generated and then use that in your Twilio settings.
You get an instant proxy to your local services to step through and debug.