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/exchanging-ice-state.ts

@@ -43,7 +43,7 @@ export class ExchangingIceState extends PeerState {
         for (const cand of candidates) {
           if (cand.candidate && cand.candidate.candidate && cand.candidate.candidate !== '') {
             try {
-              await this.peer.pc.addIceCandidate(new RTCIceCandidate(cand.candidate));
+              await this.peer.pc.addIceCandidate(new this.peer.RTCIceCandidate(cand.candidate));
               this.lastIceTimestamp = cand.createdAt;
             } catch (err) {
               console.warn('Failed to add ICE candidate:', err);