Add a biome check

[Emmet-v15]

It's useful if you want a structure in a specific biome

[BalancedOneshot]

True, most people will just world eater but for an early game farm it would be nice to specify soul sand valley.

[Emmet-v15]

adding to this, if this were to become a thing a 256x256 perimeter of the biome would be adequate (although allowing custom values would be nice too) someone else has this feature, although that only checks for normal fortresses, not crossroads