contain: invert

• The inverted containment option has been added.

Imagine your panzoom element is an image tag that spans the entire page. When contain: true is set, the image can never pan because the image is the same size as its parent. Instead, set contain: invert when initializing panzoom and you can pan the element whenever it is zoomed in. The image won't pan off-screen and you'll never see anything behind that image.