The type of event raised after an item has been added to a collection.
The event will be raised at a point of time, where the collection object is
in an internally consistent state and before the corresponding CollectionChanged
event is raised.
Note: an Update operation will fire an ItemsRemoved and an ItemsAdded event.
Note: When an item is inserted into a list (IList<T>), both
ItemInserted and ItemsAdded events will be fired.