Add PaymentChartWindow

Elwig/Helpers/Utils.cs

@@ -223,6 +223,11 @@ namespace Elwig.Helpers {
             return d.ShowDialog() == true ? d.Weight : null;
         }
 
+        public static double? ShowLinearPriceIncreaseDialog() {
+            var d = new LinearPriceIncreaseDialog();
+            return d.ShowDialog() == true ? d.Price : null;
+        }
+
         public static string? ShowDeliveryExtractionDialog(string lsnr, string name, bool single, IEnumerable<string> lsnrs) {
             var d = new DeliveryExtractionDialog(lsnr, name, single, lsnrs);
             return d.ShowDialog() == true ? d.AddTo : null;