Adds an event handler that runs when the pagination bar is changed.
A pagination bar receives a change event when a user changes the
current page by interacting with the pagination bar.
A change event is not triggered when you change a pagination bar's
current page using the currentPage property.
When a pagination bar is connected to a dataset, changing the dataset's
current page using dataset functions, such
as nextPage(), do not trigger change
events on the pagination bar.
handler(event: Event): void The name of the function or
the function expression to run when the item is ready.
This method doesn’t return any custom errors, but may return standard errors. Learn more about standard Wix errors.