Support dragging an item to the next screen
Feature summary
When you drag an icon, an affordance appears for each of the adjacent pages. If you drag the icon onto an adjacent page and release, it should behave as if you dragged it into e.g. the first position on the next screen.
At present, the user has to hold the icon over the adjacent preview until GNOME changes pages. If the system won't allow a drag to happen until the user is on the next page, there should be an affordance (e.g. an animation of the page you're hovering over beginning to take focus) to let the user know that they need to wait.