Adding Documentation

[mohammadne]

Summary

I'm new to webRTC and want to use ion-sfu in my project which includes server and clients
but I really stick into concept of the code and what is really going on in the code.

for example I don't even have idea about what is publisher and subscriber and for that I don't know how to
develop my clients in android and develop my server (I have to use MQTT signaling and using provided json-rpc and gRPC don't work)

Motivation

• It can better shows the project and make it more popular
• make it easy to use for new-commers to webRTC
• increases the ion-sfu community

[TariqueNasrullah]

I had similar issues mentioned by @mohammadne. I think it will be really helpful to include documentation for new user.

[nkonev]

For the start there is old PR #496 but without topic

• what is publisher and subscriber

Also, as the second step, personally, I adapted this example, not for Android, but for web.