Added info about support https in gelf http input

Author: malinkinsa

README.md

@@ -59,4 +59,5 @@ asyncio.run(main(message))
 - ```gelf_version``` Optional | GELF spec version (default: 1.1)
 - ```level``` Optional | The level equal to the standard syslog levels (default: 1);
 - ```scheme``` Optional | HTTP Scheme <i>for GELF HTTP input only</i> (default: http);
+- ```tls``` Path to custom (self-signed) certificate in pem format <i>for GELF HTTP input only</i> (default: None)
 - ```compress``` Optional | Compress message before sending it to the server or not <i>for GELF HTTP input only</i> (default: false)