Register missing WebRTCDataChannelJS type

(cherry picked from commit a413656e07eaf55a3b164b3fbe22abb9b7aca473)

modules/webrtc/webrtc_peer_connection_js.cpp

@@ -58,7 +58,7 @@ void WebRTCPeerConnectionJS::_on_error(void *p_obj) {
 
 void WebRTCPeerConnectionJS::_on_data_channel(void *p_obj, int p_id) {
 	WebRTCPeerConnectionJS *peer = static_cast<WebRTCPeerConnectionJS *>(p_obj);
-	peer->emit_signal("data_channel_received", Ref<WebRTCDataChannelJS>(new WebRTCDataChannelJS(p_id)));
+	peer->emit_signal("data_channel_received", Ref<WebRTCDataChannel>(memnew(WebRTCDataChannelJS(p_id))));
 }
 
 void WebRTCPeerConnectionJS::close() {

modules/webrtc/webrtc_peer_connection_js.h

@@ -52,6 +52,8 @@ extern int godot_js_rtc_pc_datachannel_create(int p_id, const char *p_label, con
 }
 
 class WebRTCPeerConnectionJS : public WebRTCPeerConnection {
+	GDCLASS(WebRTCPeerConnectionJS, WebRTCPeerConnection);
+
 private:
 	int _js_id;
 	ConnectionState _conn_state;