📚Update docs for proxy_host

Author: sinclairpaul

README.md

@@ -88,6 +88,11 @@ The private key file to use for SSL.
 
 **Note**: _The file MUST be stored in `/ssl/`, which is the default_
 
+### Option: `proxy_host`
+
+If using a reverse proxy, the domain configured for example
+`https://www.example.com`.
+
 ### Option: `remote_mysql_host`
 
 If using an external database, the hostname/address for the MYSQL/MariaDB