Notification when unable to edit components

With the progress of:

@LauGau brought up a good poin here:


One additional consideration is that, if this is implemented, there should then be a different notification for users who do not have permission to modify components (disabled via the Role Editor).

If the component is not in modify mode, and it has an innerBlocks, it should accept the drag and put the dragged thing in the innerblocks, or some child thereof.

This is a good idea and will work well if there is only one innerBlocks block.

If there are nested components with their own innerBlocks this may still work for the outer Component, but given the current selection behaviour wouldn’t work for the nested ones.