Postman Youtube playlist added

Author: optimist2309

docs/tech/backend.md

@@ -6,4 +6,6 @@ Here are some resources to start learning about API testing and automation
 
 - [Exploring Service APIs through Test Automation - Course on TAU by Amber Race](https://testautomationu.applitools.com/exploring-service-apis-through-test-automation/)
 - [What is REST?](https://developer.mozilla.org/en-US/docs/Glossary/REST)
-- [Rest API Quick Tips](https://www.restapitutorial.com/lessons/restquicktips.html)
+- [Rest API Quick Tips](https://www.restapitutorial.com/lessons/restquicktips.html)
+- [Post Man Tutorial ](https://youtube.com/playlist?list=PL6iUkDSEH9SvsgM4zyFrTnaewN65NZHAG)
+