Add proposed animation changes to onInteraction prop

[vasdee]

Allow the user to define how to animate the items during an dragmove or resizemove event. The timeline should pass in options for each of the select items such as the dx, current width, x, y ( basically rectangle properties) and the user can simply return the proposed changes to accept them, or define their own.

This should facilitate the user being able to define custom scenarios during multi-selected drag and resize events.