Fix Gin layer wrapper style for Dashboards with style overrides method

This is a quick fix for the issue

Having the following logic would be better for sure as Sascha helped with a module in Issue #3276164 by saschaeggi: Added style overrides for The Gin admin theme.

Which had to support Gin, Claro and their sub themes with the same code base.

      $active_theme = \Drupal::theme()->getActiveTheme();
      $base_themes = (array) $active_theme->getBaseThemeExtensions();

      if ($active_theme->getName() === 'gin' || array_key_exists('gin', $base_themes)) {

        // Overrides to support Gin's CSS3 variables for Light/Dark mode, Accent etc.
        $element['#attached']['library'][] = 'dashboards/assets.gin';
      }
      elseif ($active_theme->getName() === 'claro' || array_key_exists('claro', $base_themes)) {
        // Overrides to support Claro's CSS3 variables.
        $element['#attached']['library'][] = 'dashboards/assets.claro';
      }

It is for the 2.1.x branch

Testing with Support for Claro and Gin

    $active_theme = \Drupal::theme()->getActiveTheme();
    $base_themes = (array) $active_theme->getBaseThemeExtensions();
  
    if ($active_theme->getName() === 'gin'|| array_key_exists('gin', $base_themes)) {
      $build['#attributes']['class'][] = 'dashboard-gin-panel';
      $build['#attributes']['class'][] = 'gin-layer-wrapper';
    }
    elseif ($active_theme->getName() === 'claro' || array_key_exists('claro', $base_themes)) {
      $build['#attributes']['class'][] = 'dashboard-claro-panel';
      $build['#attributes']['class'][] = 'card';
    }

This patch has support for Claro too

My Dashboard sandbox with Drupal 10 - after the fix with The Claro Admin theme

This is a quick basic fix to have the Dashboards with Layout Builder works with Gin or Claro.
I would love to separate the logic and libraries, not to have dashboard-gin-panel for all admin themes.

Thank you, Erik for this so nice and important module!