add missing <?php tag

door-status-config.php

@@ -1,3 +1,5 @@
+<?php
+
 define( 'DSI_API_URL',   'https://nodered.jfig.net/api/v1/door-open' );
 define( 'DSI_CACHE_KEY', 'dsi_door_open_status' );
 define( 'DSI_CACHE_TTL', 10 );