Update SUMMARY.md

Updated Summary

Author: mr-shellychauhan

13/umbraco-commerce/SUMMARY.md

@@ -36,6 +36,8 @@
 * [Limit Order Line Quantity](how-to-guides/limit-orderline-quantity.md)
 * [Use an Alternative Database for Umbraco Commerce Tables](how-to-guides/use-an-alternative-database-for-umbraco-commerce-tables.md)
 * [Add item to Cart](how-to-guides/add-item.md)
+* [Update Cart](how-to-guides/update-cart.md)
+* [Delete item in Cart](how-to-guides/delete-item.md)
 
 ## Key Concepts