Breaks on PHP 8.0 and up

[banago]

I'm using the library to minify CSS on my workflow.

Up to PHP 7.4 it works fine, but spits this warning:

ERROR: The each() function is deprecated. This message will be suppressed on further calls 
in phar:///usr/local/bin/robo/vendor/natxet/cssmin/src/CssMin.php:2222

On PHP 8.0 and up, it fails as each() function is removed altogether from the language:

ERROR: Uncaught Error: Call to undefined function each() 
in phar:///usr/local/bin/robo/vendor/natxet/cssmin/src/CssMin.php:2222

This needs to be upgraded. What's the best way to achieve this? I'm up to put some work on this is necessary.