Add extras disk (#635)

Co-authored-by: gwleuverink <[email protected]>

Author: simonhamp

src/NativeServiceProvider.php

@@ -216,6 +216,7 @@ protected function configureDisks(): void
             'NATIVEPHP_PICTURES_PATH' => 'pictures',
             'NATIVEPHP_VIDEOS_PATH' => 'videos',
             'NATIVEPHP_RECENT_PATH' => 'recent',
+            'NATIVEPHP_EXTRAS_PATH' => 'extras',
         ];
 
         foreach ($disks as $env => $disk) {