Extending chat example to support peer discovery

[upperwal]

Extending basic chat example to include peer discovery using IPFS bootstrapping nodes and a rendezvous point to connect with other peers. This is important because current example needs manual connection by giving a peer address hence its confusing.

This example will demonstrate a simple p2p host with default transport and peer discovery mechanism and how to open a new stream once peers are found.

@bigs is also working on an example (#1) that will explore adding a custom transport (Onion transport) and using floodsub protocol for chatting. Which is more practical for chat usecase.