[Feature request] Add a way to list vehicle parts with the "Folded Volume" property

[ThePirate42]

Since there isn't a tag to filter foldable vehicle parts, it would be nice to get a list of objects with the "Folded Volume" property defined, since it's what determines the foldability.

[nornagon]

ah dang, i swear there used to be a tag for it! agree that this would be nice but unfortunately there's no clear place for this in the information architecture of the Guide, as all catalog pages are themselves "game objects" (e.g. flags go under /json_flag/FLAG_NAME). I'm not sure where idiosyncratic queries like this should go.