[MoM] Add Alien Meadow mutable map special

[Standing-Storm]

Summary

Mods "[MoM] Add Alien Meadow mutable map special"

Purpose of change

There's been occasional talk of areas with stable portals changing the terrain around them.

This is one of those.

Describe the solution

Add the "alien meadow" map special, built around a core with stable (or at least, very slowly decaying) portals and then a bunch of alien flora (and some fauna) nearby. It's not too alien--if it opened to a reality where the atmosphere was like Venus it'd just be a blasted wasteland around the portal, and if it opened to a reality where carbon couldn't form bonds, nothing from there could live in our universe--but hopefully it'll be obviously interesting and weird.

I have some ideas for plants, animals, and other odd things. Like the alien monster corpse, it's not necessarily going to have a lot of usable resources unless you like harvesting inedible alien plants.

Describe alternatives you've considered

Testing

Meadow appears, terrain and furniture (plants) exist, specials appear.

This will need another PR to add the alien fauna that spawns in the meadow (right now it's all just placeholder unviable butterflies).

Additional context