Customizer: Clarify that Collapse requires Component animations; fixes twbs#16893

[skip sauce]

Author: cvrebert

docs/customize.html

@@ -231,7 +231,8 @@ <h3>JavaScript components</h3>
         <div class="checkbox">
           <label>
             <input type="checkbox" checked value="component-animations.less">
-            Component animations (for JS)
+            Component animations (for JS)<br>
+            (includes Collapse)
           </label>
         </div>
         <div class="checkbox">