I want to manage docs on GitHub like how Auth0 does it.

https://github.com/auth0/docs

Gets converted to:

https://auth0.com/docs

Would you know the tool they use or can you suggest a tool which can achieve this rather seamlessly (ideally with a docs type theme)?

I don’t want to use Gitbook as they force to host on a separate sub domain. It’s fine if it’s a paid solution.