[SUGGESTION] Add a cvar to change the maximum number of zombies

[Chinolox]

Describe your suggestion
Currently, the maximum number of zombies that can be present on the map is 24. I can understand that due to technical limitations in the original games, this might have been the limit, but in maps with large areas or in multiplayer, this caused the map to feel empty.
I would like to modify this value to increase the difficulty (and fun).

Expected behavior
Changing the value in the console sets the new maximum capacity of zombies in the game.