RoadClasses is undocumented

[1ec5]

The jazzy docset omits RoadClasses even though it’s fully documented in the MBRoadClasses.h. Perhaps it’s because the Swift type alias and extension are undocumented?

https://github.com/mapbox/MapboxDirections.swift/blob/508ca5e92e478302c593d1ae95d41a41b0ebea62/MapboxDirections/MBRoadClasses.swift#L3-L5

/cc @samfader @vincethecoder

[1ec5]

#382 removed the RoadClass Objective-C enumeration in favor of a Swift enumeration and moved the documentation to the Swift enumeration.