code: private function findExtensionsDirectories(Container $app)
      {
          $directories = $app['config.finder']
              ->ignoreUnreadableDirs()
              ->directories()
              ->name('*Extension')
              ->in($app['app.extensions.dir'])
              ->depth('< 3')
              ->sortByName()
          ;
  
          return $directories;
      }
docs: Returns all valid extensions folders
  
  @param Container $app
  
  @return Finder