Add Node.js support via WebRTC polyfill injection

- Added WebRTCPolyfill interface for injecting WebRTC implementations
- Added wrtc option to RondevuOptions and RondevuConnectionParams
- Updated Rondevu and RondevuConnection to use injected APIs
- Added helpful error message when RTCPeerConnection is not available
- Updated README with Node.js usage examples
- Version bumped to 0.3.0

Fixes: RTCPeerConnection not defined error in Node.js

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

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

src/index.ts

@@ -20,6 +20,7 @@ export type {
   ConnectionRole,
   RondevuConnectionParams,
   RondevuConnectionEvents,
+  WebRTCPolyfill,
   // Signaling types
   Side,
   Session,