Readme suggestion + browserrepl website

Hey guys. This is incredibly awesome! Good job.

I'd like to make some improvements on the `readme` file so that developers can find the platforms and web browsers easier. Just let me know if you think its useful.

Furthermore, I think something like browserrelp.com would be awesome. Let developers run the repl online for any platforms. Does it sound interesting?

Start by reviewing the README and the repository description to understand how platforms, browsers, and the command-line REPL are currently presented. The issue needs a concrete README scope and a decision about whether an online browserrepl.com service is wanted; done would require an agreed change rather than the current open-ended suggestions.

Written by the indexing model from the issue text.