Add a itemPerSlotModifier to ContainerPrototype

[LuziferSenpai]

Hey,

it would be awesome for bigger inventories to have the option to increase the items a single slot can slot.
So similiar to how the artilerry works, as it stores 100 shells, when the shell has a stack size of 1.

I would call it something like itemPerSlotModifier or slotMultiplier.

Greetz,

Luzifer

[Rseding91]

This already exists. https://lua-api.factorio.com/latest/pro ... ntory_type with the inventory_type of "with_custom_stack_size"