It leaves out what JSON cannot carry, which a replay adds back in code:
waypoints.icon.mapping and waypoints.label.title as a function. A MapLibre expression
title serialises.HTMLImageElement, in waypoints.icon.customIcons and each waypoint
role's image. See SerializableCustomImage.
The part of a RoutingModuleConfig that survives JSON, for saving
getConfig()and replaying it withapplyConfig().