[Feature]: Highlight drop zones

Hi @artf ,

How would you recommend highlighting the components on the canvas that the selected block can be dropped into based on draggable & droppable rules? In other words, when a user starts dragging a block from the block manager I would like to highlight (add a border or inset box-shadow) the components on the canvas which it can be dropped into. This is not to replace the drop-indicator (not sure what your name for it is) which shows where the block will be placed when dragging it on the canvas but meant to complement it.

Here is an example of what I'm looking to create:

Any help would be greatly appreciated.

Thanks!