Begins or resumes playback.
The play() function plays a slideshow or playable gallery and fires a play event.
The play event handlers set on this element by the onPlay( )
function or in the Editor are called.
Notes:
When using play() on a gallery, make sure the
gallery is one where the isPlayable
capability is true.
If you change a gallery's type
to one that doesn't support play(), your code may no longer function correctly.