Add TOC to p9 (#2296)

Author: nataled

principles/fp-009-users.md

@@ -3,6 +3,7 @@ layout: principle
 id: fp-009-users
 title: Documented Plurality of Users (principle 9)
 ---
+GO TO: [Recommendations/Requirements](#recommendations-and-requirements) | [Implementation](#implementation) | [Examples/Counter‑Examples](#examples) | [Criteria for Review](#criteria-for-review) | [Feedback/Discussion](#feedback-and-discussion)
 
 ## Summary