Update README.md

Readme updated for ATF best practices

Author: Rampriya-S

README.md

@@ -12,6 +12,9 @@ Open-Sourced community contributed and owned repository for Instance Scan Defini
 
 ## Category: Manageability
 
+##Create ATFs in sub production instance
+Highly recommended practice to use ATFs for regression testing on instance upgrade and releases.
+
 ### Avoid using javascript "document" object in Portal
 Always avoid using native js "document" object for DOM manipulation in service portal. Instead we should use AngularJS equivalent capabilities to achieve the same.