Update rat.lua

Rat now spawn also on sandstone nodes (because of the new mapgen)

mods/mobs/rat.lua

@@ -45,7 +45,7 @@ mobs:register_mob("mobs:rat", {
 	end,
 })
 -- spawn on stone between 1 and 20 light, 1 in 7000 chance, 1 per area up to 31000 in height
-mobs:register_spawn("mobs:rat", {"default:stone"}, 20, 0, 10000, 1, 31000)
+mobs:register_spawn("mobs:rat", {"default:stone", "default:sandstone"}, 20, 0, 10000, 1, 31000)
 -- register spawn egg
 mobs:register_egg("mobs:rat", "Rat", "mobs_rat_inventory.png", 0)