[Force <link> instead of <style> @import url() for stylesheets] #d8 #css

1.php

/**
 * Implements hook_css_alter().
 */
function THEME_css_alter(&$css) {
  // Use <link> as opposed to <style> @import during development if
  // css preprocessing is turned off. This will allow tools like
  // BrowserSync and LiveReload to work properly.
  $preprocess_css = \Drupal::config('system.performance')->get('css.preprocess');
  if (isset($preprocess_css) && $preprocess_css === FALSE) {
    foreach ($css as $key => $value) {
      $css[$key]['preprocess'] = FALSE;
    }
  }
}