add haskell docs

Attempt to add Haskell docs, which I noticed are not currently live on DockerHub ( https://registry.hub.docker.com/_/haskell/ ).  Let me know if I have anything wrong and I'll fix it up.

ping @darinmorrison @ChristopherBiscardi
Why is this both indented _and_ fenced?  FWIW, I think the Hub's rendering engine has issues with fenced code blocks anyhow, so if you could remove the fences and just use the indent, that'd be swell. :+1: