feat(Sales Invoice): Add 'Discount Account' field in Items table

erpnext/accounts/doctype/sales_invoice_item/sales_invoice_item.json

@@ -63,6 +63,7 @@
   "finance_book",
   "col_break4",
   "expense_account",
+  "discount_account",
   "deferred_revenue",
   "deferred_revenue_account",
   "service_stop_date",
@@ -821,12 +822,18 @@
    "no_copy": 1,
    "options": "currency",
    "read_only": 1
+  },
+  {
+   "fieldname": "discount_account",
+   "fieldtype": "Link",
+   "label": "Discount Account",
+   "options": "Account"
   }
  ],
  "idx": 1,
  "istable": 1,
  "links": [],
- "modified": "2021-02-23 01:05:22.123527",
+ "modified": "2021-07-05 15:07:22.857128",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Sales Invoice Item",