We should offer ?REPL in the REPL

Thanks, @stevengj. It was not clear to me what needed to be done (I tried what was suggested by the message, adding a README.md to the /pkg directory, and re-maked the documentation, and that didn’t work), and I had asked what needed to be done on Discourse here, but did not get a reply there. I might have a shot at adding it, thanks for the explanation.