[DX] Form API #states: support 'regex' and 'less'/'greater' (than) for value comparison

I was reviewing #4509 and was playing with @indigoxela's PR on my local, trying to conditionally show/hide a warning if webp was added to the list of allowed extensions for an image field instance.

A condition like this, where the value is "static" works fine:

    '#states' => array(
      'visible' => array(
        ':input[name="instance[settings][file_extensions]"]' => array('value' => 'png, gif, jpg, jpeg, webp'),
      ),
    ),

But the goal is to check the value of the field for any occurrence of webp. Unfortunately, #states doesn't seem to support regex OOTB

With some research, I've found this article: https://evolvingweb.ca/blog/extending-form-api-states-regular-expressions which would allow something like this:

    '#states' => array(
      'visible' => array(
        ':input[name="instance[settings][file_extensions]"]' => array('regex' => array('value' => '^.*webp.*$')),
      ),
    ),