Displays an ellipsis in a breadcrumbs element instead of the middle items of the breadcrumbs trail.
The number of items hidden in the breadcrumbs trail when you use showEllipsis() depends on the values of the itemsBeforeEllipsis
and itemsAfterEllipsis properties. Any items not accounted for by those properties are hidden and replaced by an ellipsis.
For example, if your breadcrumbs trail includes 5 items and itemsBeforeEllipsis and itemsAfterEllipsis are both set to 1, the 3 middle items in the trail
are hidden when you use showEllipsis().
Using showEllipsis() changes the value of isEllipsisVisible.