chore: Add PR template. (#1943)

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,16 @@
+## Description
+
+<!-- 
+Please do not leave this blank 
+This PR [adds/removes/fixes/replaces] the [feature/bug/etc]. 
+-->
+
+## Related Tickets & Documents
+* DENG-XXXX
+* DSRE-XXXX
+
+<!-- 
+Please reference related Jira tickets, GitHub issues or Bugzilla. This repo has been 
+configured to automatically insert hyperlinks for DSRE and DENG tickets.
+See https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/managing-repository-settings/configuring-autolinks-to-reference-external-resources
+-->