Use mdoc to provide safe documentation

[gaeljw]

🤔 What's the problem you've observed?

It's important to give accurate documentation to our users and sometimes documentation is not updated, leading to pieces of code copy/pasted by users from the documentation that don't work.

✨ Do you have a proposal for making it better?

Use mdoc which is quite standard in Scala ecosystem.

📚 Any additional context?

N/A