add dependabot comment

Author: compwron

.github/dependabot.yml

@@ -21,6 +21,7 @@ updates:
       # Keep this locked to 1.77.6 until
       # bootstrap 5.3.4 is out to silence
       # sass deprecation warnings
+      # https://getbootstrap.com/docs/versions/
       - dependency-name: "sass"
         versions: ["1.77.*", "1.78.*"]