Allow running the app behind a reverse proxy (#57)
* change url to hide app behind a relative path
* pass some of ther server configuration through to the client
* serve static files and connect to socket.io correctly when a URL Prefix is set
* Revert the changes to opengraph meta tags
opengraph meta tags need to be absolute URLs
* Remove unused commented-out code
* fix background.png url
* use prefix path for open graph metadata
* Revert changes using server side url modifications
* get open graph and socket.io url from request url / window.location
* remove debug console.log
* Fix favicon when not running under "/"
* Add proxying instructions to the README
Co-authored-by: Laurent Mazet <mazet@softndesign.org>
Co-authored-by: ophir <pere.jobs@gmail.com>