Add OnInventoryItemFind hook

[WheteThunger]

Item OnInventoryItemFind(PlayerInventory inventory, int itemid)

• Called when the PlayerInventory.FindItemByItemID(int itemid) method is called. For example, when switching ammo types with the currently held weapon, when finding armor to attach to a hot air balloon, when finding a saddle to purchase a horse, and when finding a hood to cover a player's head.
• Returning an Item value cancels the default behavior, and causes PlayerInventory.FindItemByItemID(int itemid) to return that value
• Works like the List<Item> OnInventoryItemsFind(PlayerInventory inventory, int itemid) hook but for when Rust is searching for only one item instead of a list of items.