Added onSelect event listener which keeps track of when the slide index is updated. When the lightbox is opened and
when slides are moved to, this will emit the new slide index and metadata about the image (such as img src etc).
Added new showControlsBar prop so that top controls bar can be shown/hidden, depending on the value set. If set to true,
the controls bar will be shown (default), and if set to false, the controls bar will be hidden and only the close icon
will be shown
Added new closeIconBtnStyle prop so that the style of the close icon can be specified