* Decodes a lossless chunk header
* @param string $header First few bytes of the header, expected to be at least 13 bytes long
* @return bool|array See WebPHandler::decodeHeader
* Decodes a lossless chunk header
* @param string $header First few bytes of the header, expected to be at least 13 bytes long
* @return bool|array See WebPHandler::decodeHeader