Filtered hotkey slots should be "magnets"

[Peter34]

When I set a hotkey slot to filtered, e.g. filtered to normal yellow Transport Belts, then that slot should serve as a magnet and automatically suck all the Belts from my inventory into itself, so that it always presents as a full stack, when possible - i.e. until my inventory is empty of Belts.

A simple change, but one that would be very nice.

Current game behaviour is that there's no such effect until I use the last item from the slot, and then the game moves a full stack from inventory to the slot, if possible, or if not then as large a stack as it can.