Clicking on the children will cause them to be selected.
The multi-select-sk elements monitors for the addition and removal of child
elements and will update the 'selected' property as needed. Note that it
does not monitor the 'selected' attribute of child elements, and will not
update the 'selected' property if they are changed directly.
||Sent when an item is clicked and the selection is changed.
The detail of the event contains the indices of the children elements: