Adds the Smog planet to Warptorio2.

See main mod page: https://mods.factorio.com/mod/warptorio2
Planet Pack: https://mods.factorio.com/mod/warptorio_planet_pack

Credit to darkfrei for his work on the Smog / Visual Pollution Mod:
https://mods.factorio.com/mod/SmogVisualPollution