Add createDataChannel method to RondevuPeer

Adds a public method to create RTCDataChannels for sending/receiving arbitrary data between peers. The offerer can call this method before creating an offer, and the answerer will receive the channel via the existing 'datachannel' event.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/peer/index.ts

@@ -179,6 +179,15 @@ export default class RondevuPeer extends EventEmitter<PeerEvents> {
     return this.pc.addTrack(track, ...streams);
   }
 
+  /**
+   * Create a data channel for sending and receiving arbitrary data
+   * This should typically be called by the offerer before creating the offer
+   * The answerer will receive the channel via the 'datachannel' event
+   */
+  createDataChannel(label: string, options?: RTCDataChannelInit): RTCDataChannel {
+    return this.pc.createDataChannel(label, options);
+  }
+
   /**
    * Close the connection and clean up
    */