Search for item_code (#13912)

Item query can be called from custom script to search for an additional field. In this case the item_name, item_group and item_description are still searchable, but not item_code. As the item code is a must have field in search results, I have added this to the non-changable search fields in this query.
diff --git a/erpnext/controllers/queries.py b/erpnext/controllers/queries.py
index fd13c13..2ba32ce 100644
--- a/erpnext/controllers/queries.py
+++ b/erpnext/controllers/queries.py
@@ -168,6 +168,7 @@
 			and tabItem.disabled=0
 			and (tabItem.end_of_life > %(today)s or ifnull(tabItem.end_of_life, '0000-00-00')='0000-00-00')
 			and (tabItem.`{key}` LIKE %(txt)s
+				or tabItem.item_code LIKE %(txt)s
 				or tabItem.item_group LIKE %(txt)s
 				or tabItem.item_name LIKE %(txt)s
 				or tabItem.item_code IN (select parent from `tabItem Barcode` where barcode LIKE %(txt)s