Colorize output

[sol]

At least failing examples should be indicated with red.

[decentral1se]

Any movement on getting that patch in @aavogt? Would be great!

[kindaro]

I volunteer to cherry-pick the work of @aavogt and integrate it, granted that:

• #192 is merged. (There is significant refactoring of the printing mechanics.)
• There is consensus concerning #191, if we want colouring to be optional, which we likely do, because we cannot detect if the output device is capable of colour output with 100% certainty.

I will then also solve #181.

Please let me know if it's desirable.

[Congee]

Yeah, it is desired badly! 🤩 @kindaro