Function resume_route

fn resume_route(
    airships: &Airships,
    route_id: &u32,
    ctx: &mut NpcCtx<'_, '_>,
) -> usize

Calculates how to resume a route. Called when the server starts up. The airship will be at the approach final point, and this function just needs to figure out to which approach index that correlates. Returns the index of the approach to resume on.