add pull request template

PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,21 @@
+## Overview
+
+Brief description of what this PR does, and why it is needed.
+
+Closes #XXX
+
+### Demo
+
+Optional. Screenshots, `curl` examples, etc.
+
+### Notes
+
+Optional. Ancillary topics, caveats, alternative strategies that didn't work out, anything else.
+
+## Testing Instructions
+
+* How to test this PR
+* Prefer bulleted description
+* Start after checking out this branch
+* Include any setup required, such as bundling scripts, restarting services, etc.
+* Include test case, and expected output