Add support for WebRTC

[monuelo]

Description

We want to create a new concept around cast-sh instances and call them nodes. All instances can be viewed as a node and once connected they can message each other.

So, what we need to get this working:

• The node (cast-sh instance) must be able to connect with other nodes
• Each node must be able to send/receive messages from other nodes

That implementation must be via WebRTC

Note: the connection and handshake between nodes should be done via HTTP. So we also need to create new HTTP endpoints to connect and disconnect.