UDP Transport Example

[cwysong85]

I've created an example of how to use this library with the UDP transport.

https://github.com/cwysong85/sip.js-udp-example/tree/main

I plan to do the same for TCP/TLS eventually. When both are complete, I will make a fork of this repo and add those platforms. But for now, just wanted to create the repo as an example because I will be deprecating this repo: https://github.com/cwysong85/sipjs-udp which uses an old version of SIP.js.