feat: add identify protocol example

[acul71]

Description

This PR fix issue #221 and adds a new example demonstrating the usage of the identify protocol in js-libp2p. The example shows how to:

• Set up a libp2p node with the identify protocol enabled
• Create a listener node that accepts incoming connections
• Create a dialer node that connects to the listener
• Exchange and display identify information between peers

The example includes:

• A listener node that starts and displays its peer ID and multiaddrs
• A dialer node that connects to the listener using a provided multiaddr
• Automatic triggering of the identify protocol when connections are established
• Display of detailed identify information including:
  • Peer ID
  • Agent Version
  • Protocol Version
  • Supported protocols
  • Observed address
  • Listen addresses

The example is well-documented with:

• Clear setup instructions
• Detailed explanation of how it works
• Example output showing what to expect
• Node.js version requirements
• Links to relevant documentation

Notes & open questions

• The example uses Node.js version 20 or higher as required by some dependencies
• The identify protocol is configured using the new services-based approach in libp2p v2
• The example demonstrates both TCP and WebSocket transports
• The example includes mDNS peer discovery for local network discovery

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[acul71]

@achingbrain
Since I have to write interop tests to test interoperability between py-libp2p and js-libp2p I wrote this example. Will add a test soon.
Bye Luca