[MINOR] - Render file previews when using reverse proxy

[Zyrohex]

Have you checked whether this feature is not already on the project board?
Yes - there is the feature for publishing to github pages, which may provide an alternative solution, but I would still like to see support for reverse proxies with file previews.

Is your feature request related to a problem? Please describe.
Yes - I have to use emacs over X11 from a local VM to work-around some encryption issues on my work system (emacs runs very slow on my host OS as a result making it unusable), but I cannot access the graph since its being hosted from the VM rather than my local system. Configuring a reverse proxy server works for the most part that the website is viewable, and you can see the graph, but file previews fail to render their content.

Describe the solution you'd like
Add support so that the file previews can be served over a reverse proxy.

Additional context
Simple reverse proxy config:

server {
        listen   80;
        server_name     192.168.1.181;

        location / {
                proxy_pass      http://localhost:35901/;
                proxy_set_header Host $http_host;
                proxy_set_header X-Real-IP $remote_addr;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }
}