Add WebRTC polyfill support for Node.js environments

Added optional polyfill parameters to RondevuOptions to support Node.js:
- RTCPeerConnection: Custom peer connection implementation
- RTCSessionDescription: Custom session description implementation
- RTCIceCandidate: Custom ICE candidate implementation

This allows users to plug in wrtc or node-webrtc packages for full
WebRTC support in Node.js environments. Updated documentation with
usage examples and environment compatibility matrix.

Version bumped to 0.7.4

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

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

src/peer/state.ts

@@ -27,7 +27,7 @@ export abstract class PeerState {
   async handleIceCandidate(candidate: any): Promise<void> {
     // ICE candidates can arrive in multiple states, so default is to add them
     if (this.peer.pc.remoteDescription) {
-      await this.peer.pc.addIceCandidate(new RTCIceCandidate(candidate));
+      await this.peer.pc.addIceCandidate(new this.peer.RTCIceCandidate(candidate));
     }
   }