Update PULL_REQUEST_TEMPLATE.md

updating the template for future addition of test cases

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,6 +7,7 @@ Please describe the motivation behind the pull request, whether it enables a new
 Please put an `x` into the boxes that apply. You can also fill these out after creating the PR. If you're not sure, please don't hesitate to ask.
 
 - [ ] I have added tests relevant to the introduced functionality, and the unit tests are passing locally
+- [ ] I have added the test to REGRESSION_TESTS list defined at the top of CMakeLists.txt in tests/CMakeLists.txt, IF THE TEST takes more than 30 seconds to run.
 - [ ] I have added inline documentation which enables the maintainers with understanding the motivation
 - [ ] I have removed the stale documentation which is no longer relevant after this pull request
 - [ ] (If this change is user-facing) I have added release notes which provide the end users with a brief summary of the improvement from this pull request