Add example for the release note section in pr template
The format of the release note section in a pr description should be in
a list. It looks best like that in the generated release note :D
@@ -38,9 +38,13 @@ Mainly, pointers to review the PR, and how they can test it.
## Release Note
<!--
-If needed, you can leave a detailed description here which will be used to
-generate the release note for the next version of Concourse. The title of the
-PR will also be pulled into the release note.
+If needed, you can leave a list of detailed descriptions here which will be
+used to generate the release note for the next version of Concourse. The title
+of the PR will also be pulled into the release note.
+
+Example:
+* Reticulating splines is the new process Concourse uses to create the network
+ of lines between jobs.
-->
## Contributor Checklist
