Add payment document import

Hcs.Client/Client/UniClient.cs

@@ -11,6 +11,8 @@ namespace Hcs.Client
     /// </summary>
     public class UniClient : ClientBase
     {
+        public BillsApi Bills => new(this);
+
         public DeviceMeteringApi DeviceMetering => new(this);
 
         public HouseManagementApi HouseManagement => new(this);