scrollLeftItem
fun scrollLeftItem(line: MutableProvider<Int>, on: ItemProvider = DefaultGuiItems.TP_ARROW_LEFT_ON.clientsideProvider, off: ItemProvider = DefaultGuiItems.TP_ARROW_LEFT_OFF.clientsideProvider): Item
A UI item for scroll guis that decrements line on left-click. Uses on as item provider if it is possible to scroll left, otherwise uses off.