Clean up creative inventory tabs a little

mods/throwing/arrow.lua

@@ -1,6 +1,7 @@
 minetest.register_craftitem("throwing:arrow", {
 	description = "Arrow",
 	inventory_image = "throwing_arrow_inv.png",
+	groups = { ammo=1, ammo_bow=1 },
 })
 
 minetest.register_node("throwing:arrow_box", {

mods/throwing/init.lua

@@ -36,6 +36,7 @@ minetest.register_tool("throwing:bow", {
 		itemstack:add_wear(wear)
 		return itemstack
 	end,
+	groups = {weapon_ranged=1,},
 	on_use = function(itemstack, user, pointed_thing)
 		local wear = itemstack:get_wear()
 		itemstack:add_wear(wear)