⭐ Design a UI to support favouriting a particular route/heading combination on a stop

[emilymclean]

This would also require updating the Favourite model to optionally support a heading parameter.

[emilymclean]

This would be in view of allowing the quick viewing of the next vehicle of a route you're interested in at a stop you use regularly. I.e., if I were to use the belco interchange to travel to civic for work, it might be useful to see when the next bus of that route/heading/stop were arriving.