kts.AddMonster – add a monster to the dungeon
result = kts.AddMonster(pos, monster_type)
If possible, a monster of the given MonsterType will be created, and placed into the dungeon at position pos.
If not possible (for example, because there is no room at position pos), then nothing will happen.
If placement succeeds, a Creature userdata object, representing the new monster, will be returned.
Otherwise, nil is returned.
If any of the input parameters are invalid then an error is raised.