Mention branch protection ordering (#6406)

Co-authored-by: Jack Berg <jberg@newrelic.com>

.github/repository-settings.md

@@ -17,6 +17,11 @@ Repository settings in addition to what's documented already at
 
 ## Branch protections
 
+The order of branch protection rules
+[can be important](https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/defining-the-mergeability-of-pull-requests/managing-a-branch-protection-rule#about-branch-protection-rules).
+The branch protection rules below should be added before the `**/**` branch protection rule
+(this may require deleting the `**/**` rule and recreating it at the end).
+
 ### `main`
 
 * Require branches to be up to date before merging: UNCHECKED