message: docs(decision-tree-widget): Add header to decision tree widget section
  so it's more noticeable
diff: @@ -15,6 +15,8 @@ RxJS is a library for reactive programming using Observables, to make it easier
  - - -
  +### Find the right Operator
  +
  <div class="decision-tree-widget"></div>
  **Hint: open your DevTools to experiment with RxJS.**
  