add washboard to antique spawns

[anoobindisguise]

Summary

Balance "washboard spawns in antique stores"

Purpose of change

Washboards are archaic, fitting to spawn in antique stores. They were pretty rare if not made by the player character and I wanted to expand their availability without using crafting.

Describe the solution

Washboards are added to the antique loot pool. This means it will also show up in some other places like wooden forts and pawn shops.

Describe alternatives you've considered

Make antique stores more full of stuff, as they have basically no reason to be looted by marauding zombies-to-be and thus would be replete with 'stuff'.

Testing

Additional context