Add support for downloading critical CSS from an URL

The alter hook implementation would look like this:

/**
 * Implements hook_critical_css_file_paths_suggestion_alter().
 */
function my_module_vite_critical_css_file_paths_suggestion_alter(array &$file_paths, ?ContentEntityInterface $entity): void {
  $file_paths[] = "http://localhost:3000/dev/sass/default-critical.scss";
}

Merged, thanks @dieterholvoet