Showing numbers in SVG boxes instead of just colors

[j-silv]

Hello!

First off, thank you so much for preparing these puzzles. They have really helped me step up my PyTorch tensor game.

I was wondering if you saw an issue with adding the numbers directly to each square? When I was going through the puzzles, sometimes it was really hard to tell the difference between a lightly shaded gold box and a more deeply shaded one.

For example, doing something like this:

I'm happy to open up a pull request, just wanted to know if you were against this idea.