Add freehand painting for road markings

It would be amazing if we could draw dashed lines, coloured road hatching, road edge lines etc by driving a dedicated painting vehicle along the finished road.

I imagine this would be quite challenging for the player to do a perfect job - imo this only makes it more fun, but there could be some sort of assist functionality to make the lines neater.

Bonus points if the automated convoy trucks respect these lines in some way, but that might be a stretch 😁