js-overlay-close was already bound to hide() + firing a close event, which is what is picked up by the gallery lightbox for unbinding event handlers. This PR just moves that code to it's own method so the escape button can use it too. This seemed like the least disturbing fix. Though tbh I'm not sure why there is a distinction drawn between hide and close. The close event is only sent after hiding in response to clicking the close icon, yet there is no way for users of the class to trigger the close event in response to other actions (e.g. escape button or browser history). So the event only really indicates that the close icon has been clicked, which doesn't seem to provide any utility above the hide event and causes confusion (as evidenced by this bug).

Unbinding on hide event makes more sense, so will change to that. Thanks