Update the PR template to include a documentation checklist item. (#3629)

Signed-off-by: bgravenorst <byron.gravenorst@consensys.net>

.github/pull_request_template.md

@@ -7,6 +7,11 @@
 <!-- Please link to fixed issue(s) here using format: fixes #<issue number> -->
 <!-- Example: "fixes #2" -->
 
+## Documentation
+
+- [ ] I thought about documentation and added the `doc-change-required` label to this PR if
+    [updates are required](https://wiki.hyperledger.org/display/BESU/Documentation).
+
 ## Changelog
 
 - [ ] I thought about the changelog and included a [changelog update if required](https://wiki.hyperledger.org/display/BESU/Changelog).