Consider using data-URI to embed how_tor_works_thumb.png image into tor-exit-notice.html
We can only serve a single HTML file with
DirPortFrontPage configuration option. Currently we provide an exit notice file in tor-exit-notice.html, which embeds an image with basic Tor network schematics from Tor website. We may want to use data-URI format (as described in RFC 2397) to hardcode this image into HTML and avoid loading it from external webserver.