New setting to prevent Swapping backpack to offhand.

[ClickErrorxD]

Ability to disable/enable the ability to press the offhand button to put the backpack in the offhand.

Feature description
I would like to prevent players from pressing the swap hand button while holding the backpack item. This allows them to move the backpack throughout the hotbar, even though we enabled the setting to keep it in one slot.

How the feature is useful
It causes issues with server hardcoded items in the hotbar, ie: server menu