feat: use private/components/stage.start.php if exists (#1266)

Change-Id: I6ea6a52be7f59c19bf61f802b961d13b23620c8b

Author: andi34

index.php

@@ -58,8 +58,10 @@
     </div>
 <?php endif; ?>
 <?php
+$privateStageStart = PathUtility::getAbsolutePath('private/components/stage.start.php');
+$stageStart = PathUtility::getAbsolutePath('template/components/stage.start.php');
 
-include PathUtility::getAbsolutePath('template/components/stage.start.php');
+include file_exists($privateStageStart) ? $privateStageStart : $stageStart;
 if (!$config['ui']['selfie_mode']) {
     include PathUtility::getAbsolutePath('template/components/stage.loader.php');
     include PathUtility::getAbsolutePath('template/components/stage.results.php');