Adds an event handler that runs when the playback is started or restarted.
A video in a video box is played when a site visitor clicks the video box's
play button or by calling its play() function.
handler(event: Event): void The name of the function or
the function expression to run when the video in the video box is played.
This method doesn’t return any custom errors, but may return standard errors. Learn more about standard Wix errors.