Add extractor script for BlaBlaCar Bus
Tested with tickets from blablacar.nl.
Depends on !39 (merged)
Any improvement suggestions welcome, this is my first extractor script :) I can also provide sample data for this after my trip.
It's possible that tickets from blablacar.fr and blablacar.co.uk (that's the other languages/domains I'm aware of) require some adjustments also. The QR code seems to contain the same data, but I (obviously) haven't tried checking in with it yet.