feat: new hook `fields_for_group_similar_items` to group additional fields for print formats (#40831)

diff --git a/erpnext/hooks.py b/erpnext/hooks.py
index b3cfb35..9c1521a 100644
--- a/erpnext/hooks.py
+++ b/erpnext/hooks.py
@@ -634,3 +634,5 @@
 }
 
 export_python_type_annotations = True
+
+fields_for_group_similar_items = ["qty", "amount"]