Add 'draft' note to top of fp-013-notifications.md (#2283)

Author: nataled

principles/fp-013-notification.md

@@ -4,6 +4,9 @@ id: fp-013-notification
 title: Notification of Changes (principle 13)
 ---
 
+**THE TEXT HEREIN IS A DRAFT, PENDING FINAL VETTING**
+----------------------------------------------------
+
 Summary
 -------