docs: add scheme to nginx proxy configuration

docs/install/nginx.md

@@ -29,6 +29,8 @@ server {
 
   location @proxy {
     proxy_set_header Host $host;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+		proxy_set_header X-Forwarded-Proto $scheme;    
     proxy_pass http://127.0.0.1:13120;
   }
 }