Example mob mass addition file.  Add mobs with the pattern below and rename file to MassAdditionMobs.csv
Line, Category*, Class**, Namespace:Mob, Weight, Mingroup , Maxgroup

1, A, MONSTER, minecraft:phantom, 10, 1, 4

* A, O, N, E for All, Overworld, Nether, The End
** MONSTER,CREATURE,AMBIENT
