PHPCS 4.x drops support for scanning JS/CSS files. In PHPCSExtra, the only sniff which explicitly has JS/CSS support is the `Univeral.WhiteSpace.PrecisionAlignment` sniff. In the next major, the scanning of JS/CSS files should be removed. Note: as the sniff _also_ scans PHP files, this should not trigger deprecation notices/errors from PHPCS, so there is no urgency.