Support for Shared Element Transitions

[davidkpiano]

Currently, flipjs supports implementing the FLIP technique for a single element that changes position due to a class change. However, a common use-case (similar to Android's Shared Element Activity Transitions) is that:

• The final node is nearly equivalent to the initial node, save for differences in position/size.
• The final node is not the same node as the initial node.

One strategy I've been using is [data-flip="foo"] on both the initial and final nodes, so that I can:

• getBoundingClientRect() on the initial (currently visible) node
• execute the code that removes the initial node and displays the final node
• getBoundingClientRect() on the final (now visible) node
• execute FLIP.

Perhaps we can supply an argument to last(...) that allows us to specify the new shared node?