code: public function handle(Context $context)
      {
          static $wsList = array("\r", "\n", "\r\n", "\t", " ");
          while ($context->hasNext()) {
              $current = $context->current();
              if (!in_array($current, $wsList)) {
                  break;
              }
              $context->next();
          }
      }
docs: 文字 %x20, %x09, %x0A, %x0D を読み飛ばします.
  
  @param Context $context