Update PR template to include doc issue ref (dapr#1351)

Initiative to ensure docs are in line to current feature set

Co-authored-by: Aman Bhardwaj <[email protected]>

.github/pull_request_template.md

@@ -16,6 +16,6 @@ Please make sure you've  completed the relevant tasks for this PR, out of the fo
 * [ ] Created/updated tests
 * [ ] Unit tests passing
 * [ ] End-to-end tests passing
-* [ ] Extended the documentation
-* [ ] Specification has been updated
-* [ ] Provided sample for the feature
+* [ ] Extended the documentation / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#_[issue number]_
+* [ ] Specification has been updated / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#_[issue number]_
+* [ ] Provided sample for the feature / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#_[issue number]_