[Feature Request] Change `UploadService.DisplayURL` to `UploadService.ProxyURL`

[OoLunar]

Currently ImageFrame requires an entire subdomain by enforcing POST /upload to the root of the (sub)domain. Instead I believe it would make more sense if the proxy url was prepended to any other paths the embedded web server requires.

Example config:

# ImageFrame's convenient upload system where you can upload directly through an embedded web server
UploadService:
  # Changing this value requires a restart
  Enabled: true
  # This is the base URL the plugin uses.
  ProxyURL: https://example.com/image_frame/
  WebServer:
    # Address in which the webserver binds to, defaults to 0.0.0.0
    # Use 127.0.0.1 to limit to local access
    # Changing this value requires a restart
    Host: 0.0.0.0
    # Port in which the webserver is hosted, make sure it is not blocked by your firewall
    # Changing this value requires a restart
    Port: 8517

Creating an upload link would look like: GET example.com/image_frame/?user=0000-0000-0000-0000
Uploading the image body would look like: POST example.com/image_frame/upload?...

[LOOHP]

I'm not sure I understand what the suggestion is fully. Currently the DisplayURL is just for the clickable link in the chat message for the player. The web server itself just listens to the root path for GET and the root path + /upload for POST on whatever it is hosted on.