Add categorize field in PR template (#592)

Author: AleksandarSavchev

.github/pull_request_template.md

@@ -1,3 +1,12 @@
+**How to categorize this PR?**
+<!--
+Please select the kind of this pull request, e.g.:
+/kind enhancement
+Tide will not merge your PR, if it is missing a `kind/*` label.
+"/kind" identifiers:    api-change|bug|cleanup|discussion|enhancement|epic|impediment|poc|post-mortem|question|regression|task|technical-debt|test
+-->
+/kind TODO
+
 **What this PR does / why we need it**:
 
 **Which issue(s) this PR fixes**: