changed
Description:
This signal is emitted when back_forward_list changes.
 This happens when the current item is updated, a new item is added or one or more items are removed. Note that both item_added 
      and items_removed can null when only the current item is updated. Items are only removed when the
       list is cleared or the maximum items limit is reached.
Parameters:
| item_added | the BackForwardListItem added or null | 
| items_removed | a List of BackForwardListItem<!-- -->s |