Add a Toolbelt Inventory Slot

Just like the offhand, add another inventory slot for passive item usage.

When travelling in caves, equipping a Lantern to the Toolbelt slot would function as a mobile dynamic light source, removing the need to place torches every few chunks and also avoiding the performance issues that would arise by making all light sources dynamic. It could also be used to carry a Bundle, a Totem of Undying, or even Potions.

You should also be able to equip a Spyglass in this slot and introduce a built-in hotkey for it.