Rtl documentation (#2141)

* Hide vertically hidden ranged items in groups that are not visible
* Add rtl to timeline options docs
* Fix misspelling
* Update RangeItem.js

docs/timeline/index.html

@@ -895,6 +895,12 @@ function (option, path) {
       <td>Orientation of the timeline items: 'top' or 'bottom' (default). Determines whether items are aligned to the top or bottom of the Timeline.</td>
     </tr>
 
+     <tr>
+      <td>rtl</td>
+      <td>boolean</td>
+      <td><code>false</code></td>
+      <td>If true, the timeline will be right-to-left.</td>
+    </tr>
 
     <tr>
       <td>selectable</td>

lib/timeline/component/Group.js

@@ -180,7 +180,6 @@ Group.prototype.redraw = function(range, margin, restack) {
 
   // recalculate the height of the subgroups
   this._calculateSubGroupHeights();
-
   this.isVisible = this._isGroupVisible(range, margin);
 
   // reposition visible items vertically
@@ -276,6 +275,7 @@ Group.prototype._calculateSubGroupHeights = function () {
  * check if group is visible
  * @private
   */
+
 Group.prototype._isGroupVisible = function (range, margin) {
   var isVisible = 
   (this.top <= range.body.domProps.centerContainer.height - range.body.domProps.scrollTop + margin.axis)