Better route indication

[rozmy]

That's a bit overkill from implementation perspective so feel free to close it.

It would be nice to draw the route between each step as on this mockup below. This improves the readability but introduces a load of edgecases to cover like:

• intersecting lines
• intersection below highlighted cells
• longer buffers could be complicated visually (this example is from your github screenshot, so that's the best case IMO)

[cxcorp]

The implementation isn't that overkill - the image on the right is exactly how I render the results in my own project. Example here. Most of the fluff is just figuring out a proper font width for the canvas. Handling intersections is definitely an annoying edge-case though for the solver's optimizer, but it's doable!