Added WebRTC stuff - Needs Testing.

RelayClient/Models/SocketRtcSignalMessage.cs

@@ -0,0 +1,13 @@
+namespace RelayClient.Models;
+
+public class SocketRtcSignalMessage
+{
+    public required string Type { get; set; } // encrypted_rtc_signal
+    public required string SenderUsername { get; set; }
+    public required string RecipientUsername { get; set; }
+
+    public required string CipherText { get; set; }
+    public required string Nonce { get; set; }
+    public required string Tag { get; set; }
+    public required string EncryptedKey { get; set; }
+}