Add docker file example to easily deploy to the cloud

[hmbenhaim]

Hi first of all thank you for your hard work on this project. I wander if you have any docker file that you can include in this project with all the depends and everything needs to deploy this server to the cloud because it's really hard to get Intu this code and write the docker file Thank you

[cloudwebrtc]

This is a good idea, I think it will not be too difficult because this repo has only one main.go and a few necessary ports to be exposed.

[1993alexey]

I wrote this dockerfile for my production use case. https://github.com/flutter-webrtc/flutter-webrtc-server/issues/91