Update README board documentation

Add `payload` param to callback function handleDragEnd

Author: tatosjb

README.md

@@ -97,7 +97,7 @@ This is the container component that encapsulates the lanes and cards
 | handleDragStart     | function | Callback function triggered when card drag is started: `handleDragStart(cardId, laneId)`                                       |
 | handleDragEnd       | function | Callback function triggered when card drag ends: `handleDragEnd(cardId, sourceLaneId, targetLaneId, position, cardDetails)`                 |
 | handleLaneDragStart | function | Callback function triggered when lane drag is started: `handleLaneDragStart(laneId)`                                           |
-| handleLaneDragEnd   | function | Callback function triggered when lane drag ends: `handleLaneDragEnd(laneId, newPosition)`                                      |
+| handleLaneDragEnd   | function | Callback function triggered when lane drag ends: `handleLaneDragEnd(laneId, newPosition, payload)`                                      |
 | cardDragClass       | string   | CSS class to be applied to Card when being dragged                                                                             |
 | laneDragClass       | string   | CSS class to be applied to Lane when being dragged                                                                             |
 | onLaneScroll        | function | Called when a lane is scrolled to the end: `onLaneScroll(requestedPage, laneId)`                                               |