Review Mojo's priorities

• I have read the roadmap and priorities and I believe this request falls within the priorities.

What is your request?

Providing a Docker image with the REPL would ease installation on non-supported platforms.

What is your motivation for this change?

I tried installing Mojo on Arch Linux but I encountered some difficulties. There's also an open issue about installing on Arch, #572. An official Docker image would solve the problem for Arch, any other non-Debian-based distros, and any OS supported by Docker.

Any other details?

I created my own Dockerfile to solve the issue and it works. I can provide it via a pull request if you're interested.