Page does not scroll when dragging images in reorder mode

[dschwen]

When using the reorder (ranking) mode to reorder thumbnails on a page it would be nice if the page scrolled when the dragged image touched either the top or bottom borders of the viewport. This is expected UX. Without this feature dragging an image from the bottom of a long page to the top requires many steps of picking the thumbnail up dragging it up a few rows, dropping it, scrolling the page up, picking the thumbnail up again, etc.

[MichaelNMaggs]

This should actually be high priority if ranking rounds are being used, as in Wiki Loves Africa. It makes the ranking system almost unusable if there are multiple screens of images. (Previously reported by email on 23/3/17)

[MichaelNMaggs]

This one is a really annoying problem!