Add additional params to cpp init request (#195)

Craftgate/Request/InitCheckoutPaymentRequest.cs

@@ -34,6 +34,6 @@ public class InitCheckoutPaymentRequest
         public IList<CustomInstallment> CustomInstallments { get; set; }
         public IList<PaymentItem> Items { get; set; }
         public FraudCheckParameters FraudParams { get; set; }
-
+        public Dictionary<string, object> AdditionalParams { get; set; }
     }
 }