add pull request template

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,35 @@
+**What type of PR is this?**
+> Uncomment only one ` /kind <>` line, hit enter to put that in a new line, and remove leading whitespaces from that line:
+>
+> /kind api-change
+> /kind backend-change
+> /kind ui-change
+> /kind bug
+> /kind cleanup
+> /kind design
+> /kind documentation
+> /kind failing-test
+> /kind feature
+> /kind flake
+
+**What this PR does / why we need it**:
+
+**Which issue(s) this PR fixes**:
+<!--
+*Automatically closes linked issue when PR is merged.
+Usage: `Fixes #<issue number>`, or `Fixes (paste link of issue)`.
+_If PR is about `failing-tests or flakes`, please post the related issues/tests in a comment and do not use `Fixes`_*
+-->
+Fixes #
+
+**Special notes for your reviewer**:
+
+**Does this PR introduce a user-facing change?**:
+<!--
+If no, just write "NONE" in the release-note block below.
+If yes, a release note is required:
+Enter your extended release note in the block below. If the PR requires additional action from users switching to the new release, include the string "action required".
+-->
+```release-note
+
+```