Include lint validation as a requirement in the PR template

Author: renonick87

.github/PULL_REQUEST_TEMPLATE.md

@@ -9,6 +9,7 @@ This PR makes **[no / minor / major]** API changes.
 
 ### Testing Plan
 - [ ] I have verified that I have not introduced new warnings in this PR (or explain why below)
+- [ ] I have verified that this PR passes lint validation
 - [ ] I have run the unit tests with this PR
 - [ ] I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).