fix config

Sources/Punchnet/SDLConfiguration.swift

@@ -13,6 +13,11 @@ public class SDLConfiguration {
     public struct StunServer {
         public let host: String
         public let ports: [Int]
+        
+        public init(host: String, ports: [Int]) {
+            self.host = host
+            self.ports = ports
+        }
     }
     
     // 当前的客户端版本