code: public static function registerApp(string $namespace, string $path = null)
      {
          $namespace = rtrim($namespace, '\\');
          if ($path == null) {
              $path = constant('STRAY_PATH_APPS') . str_replace(
                  '_',
                  DIRECTORY_SEPARATOR,
                  str_replace('\\', DIRECTORY_SEPARATOR, $namespace)
              );
          }
          self::$namespaces[$namespace] = $path;
          self::$applications[] = $namespace;
      }
docs: Add a namespace to the recognized ones.
  Use this for files in the _apps_ directory.
  
  @static
  @param string $namespace new namespace
  @param string $path      custom files path if needed