Update to latest spec of GTFS

[pietercolpaert]

The base spec changed a lot and this is not reflected in the Linked GTFS vocabulary.

Update it: https://developers.google.com/transit/gtfs/reference

[derhuerst]

I think once google/transit#127 is done and there's a machine-readable schema, updating Linked GTFS could be done semi-automatically.

[pietercolpaert]

Ah, how I wish they would just publish an RDF version of their terms 😅

[pietercolpaert]

I wonder whether we can just write a github action that translates the machine readable schemas to gtfs.ttl and maybe even a SHACL shape