Add {$CADDY_EXTRA_CONFIG} (#1017)

Author: tm1000

src/Commands/stubs/Caddyfile

@@ -8,6 +8,8 @@
 	}
 }
 
+{$CADDY_EXTRA_CONFIG}
+
 {$CADDY_SERVER_SERVER_NAME} {
 	log {
 		level {$CADDY_SERVER_LOG_LEVEL}