Update pull_request_template.md

Author: jackzhxng

.github/pull_request_template.md

@@ -1,9 +1,9 @@
 ### Summary
-[PLEASE REMOVE] Describe the goal of this PR and add any relevant context.
+[PLEASE REMOVE] See [CONTRIBUTING.md's Pull Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests) for ExecuTorch PR guidelines.
 
 [PLEASE REMOVE] If this PR closes an issue, please add a `Fixes #<issue-id>` line.
 
-[PLEASE REMOVE] If this PR introduces a fix or feature that should be the upcoming release notes, please add a "Release notes: <area>" label.
+[PLEASE REMOVE] If this PR introduces a fix or feature that should be the upcoming release notes, please add a "Release notes: <area>" label. For a list of available release notes labels, check out [CONTRIBUTING.md's Pull Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests).
 
 ### Test plan
 [PLEASE REMOVE] How did you test this PR? Please write down any manual commands you used and note down tests that you have written if applicable.