Add demo

Src/Asp.NetCore2/PgSqlTest/Demo/Demo2_Updateable.cs

@@ -66,10 +66,13 @@ namespace OrmTest
             var result8 = db.Updateable<Order>(it => it.Name == "Name").Where(it => it.Id == 1).ExecuteCommand();
             var result81 = db.Updateable<Order>().SetColumns(it => it.Name == "Name" ).Where(it => it.Id == 1).ExecuteCommand();
             //
+            var result61 = db.Updateable<Order>()
+           .InnerJoin<Custom>((x, y) => x.CustomId == y.Id)
+           .SetColumns((x, y) => new Order() { Name = y.Name, Price = y.Id })
+           .Where((x, y) => x.Id == 1)
+           .ExecuteCommand();
 
-
-
-
+             
             /*** 3.by Dictionary ***/
             var dt = new Dictionary<string, object>();
             dt.Add("id", 1);