[ENHANCEMENTS] Add support for PROXY PROTOCOL

[xenadmin]

Is your feature request related to a problem? Please describe.
HAPROXY, NGINX, Caddy and Traefik all support PROXY PROTOCOL.
Nginx Proxy Manager and Zoraxy don't.
It would be nice, if the two Docker Reverse Proxys with a beginner-friendly GUI, would support it.

Describe the solution you'd like
I would like for Zoraxy to support PROXY PROTOCOL for example for:
https://stalw.art/docs/server/reverse-proxy/proxy-protocol

Describe alternatives you've considered
Not using Zoraxy ;-)
Currently, the typical alternative would be using Caddy or Traefik.
Or classic NGINX or HAPROXY.

Additional context
#363

[jwgn]

+1
Please implement this. I am also using Stalwart behind Zoraxy.