Merge pull request #5203 from acpana/acpana/extend-template

chore: update template

Author: google-oss-prow[bot]

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,4 +1,4 @@
-### Change description
+### BRIEF Change description
 
 <!--
 Describe what this pull request does.
@@ -12,6 +12,8 @@ For example: "Fixes #858"
 -->
 Fixes #
 
+#### WHY do we need this change?
+
 #### Special notes for your reviewer:
 
 #### Does this PR add something which needs to be 'release noted'?