Add query optimization scripts and results

sql/get_max_quantity.sql

@@ -0,0 +1,12 @@
+-- query optimization - task 1
+-- changes:
+--   interpreted quantity as the number of items in an order, because I assumed that Little lemon wants
+--   orders à la carte instead of fixed menus
+
+create procedure GetMaxQuantity () -- noqa: disable=CP03
+select count(OI.OrderItemID) as MaxQuantityInOrder
+from MenuItems as MI
+inner join OrderItems as OI on MI.MenuItemID = OI.MenuItemID
+group by OI.OrderID
+order by MaxQuantityInOrder desc
+limit 1