The demo is not working between peers on completely different networks

[marek-sykora-zf]

Steps to reproduce:

1. take you mobile phone and ensure you are connected using operator, e.g. 4G network, and not local network
2. open browser on our mobile, make it as receiver, so visit https://jmcker.github.io/Peer-to-Peer-Cue-System/receive.html
3. PC: open browser on your PC, make it as sender, so visit https://jmcker.github.io/Peer-to-Peer-Cue-System/send.html
4. PC: type proper ID from receiver part and finish connection
5. PC: try to send some message

Expected result: the chat is working, you can send and read messages
Current result: it works only if receiver and sender are on the same or nearby network

The issue is very probably caused by TURN/STUN server.