chore(gantt): clarify popup editing behavior (#805)

Author: radkostanev

components/gantt/gantt-tree/editing.md

@@ -530,6 +530,7 @@ There are a few considerations to keep in mind with the CUD operations of the tr
 
 * While editing, the Gantt creates a **copy of your original object** which has a **different reference**. You receive that copy in the `OnUpdate` event handler.
 
+* Double clicking on a task within the Timeline part of the component will always trigger Popup edit of the said task, even if edit mode is set to Inline or Incell.
 
 ## See Also
 

components/gantt/timeline/editing.md

@@ -158,7 +158,7 @@ The Gantt component allows you to initiate editing from its Timeline component i
 
 ## Popup Editing
 
-You can invoke popup editing of a task by double clicking on it. A Popup container will be displayed containing the default editors for the fields defined in the Gantt.
+You can invoke popup editing of a task by double clicking on it. A Popup container will be displayed containing only the default editors associated with a Gantt Task. No additional fields defined in the Gantt will be editable through this form.
 
 If you have set the corresponding handlers, you will be able to Save or Cancel the editing operation, or Delete the record.