Add possibility to use nginx reverse proxy

[mahmoud-ashi]

In the documentation, you mention how you can add a new site in nginx. It would be nice to also explain how to achieve the same with a reverse proxy location in the default site. I guess you would need to also enable something like "/skep" at the end of the URL "http://domain.exmaple.com:8080/skep".

[bobf]

@mahmoud-ashi I will try to set this up and publish the config. If you have a working config then feel free to paste it here/make a PR for the README.