message: add animation to chevron opening and closing
diff: @@ -270,6 +270,8 @@ $outcome-not-applicable-summary-color: $neutral-outcome;
  content: '';
  position: absolute;
  margin-top: 6px;
  + transform-origin: 50% 50%;
  + transition: transform 0.1s linear 0s;
  }
  summary::-webkit-details-marker {
  