.github: Add release notes block to pull request template

Signed-off-by: Stephen Augustus <saugustus@vmware.com>

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,10 +7,12 @@ Thank you for sending a pull request! Here some tips for contributors:
 4. If the Pull Request is a work in progress, make use of GitHub's "Draft PR" feature and mark it as such.
 -->
 
-**Overview**:
+#### Overview
+
 <!-- Describe your changes briefly here. -->
 
-**What problem does it solve?**:
+#### What this PR does / why we need it
+
 <!--
 - Please state in detail why we need this PR and what it solves.
 - If your PR closes some of the existing issues, please add links to them here.
@@ -18,4 +20,16 @@ Thank you for sending a pull request! Here some tips for contributors:
   Usage: "Closes #<issue number>", or "Closes (paste link of issue)"
 -->
 
-**Special notes for a reviewer**:
+#### 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
+
+```