[#14] Windows: Add DeliveryScheduleAdminWindow

Elwig/App.xaml.cs

@@ -292,6 +292,10 @@ namespace Elwig {
             return w;
         }
 
+        public static DeliveryScheduleAdminWindow FocusDeliverySchedule() {
+            return FocusWindow<DeliveryScheduleAdminWindow>(() => new());
+        }
+
         public static PaymentVariantsWindow FocusPaymentVariants(int year) {
             return FocusWindow<PaymentVariantsWindow>(() => new(year), w => w.Year == year);
         }