ci(update): add notes to PR body about modifying schemas (#694)

#691 (comment)

.github/workflows/update.yml

@@ -38,6 +38,12 @@ jobs:
             messages accordingly to trigger the right release, see [our commit
             message
             conventions](https://github.com/octokit/webhooks/blob/master/CONTRIBUTING.md#merging-the-pull-request--releasing-a-new-version).
+
+            If there are any new events added, follow the [steps outlined](https://github.com/octokit/webhooks/blob/master/CONTRIBUTING.md#creating-a-new-schema)
+            in order to create the required schemas.
+            
+            If there were only description updates, or new properties added, simply modify the appropriate schemas and commit them to this PR.
+            Don't forget to generate the types as well.
           branch: webhooks-update
           author: Octokit Bot <octokitbot@martynus.net>
           path: cache/