Make drowl_paragraphs Photoswipe 5 compatible

The problem is, that we currently attach photoswipe twice. Once through this code inside the drowl_paragraphs module file:

/**
 * Helper function for image paragraph types with field "image_zoomable".
 */
function _drowl_paragraphs_types_preprocess_paragraph_image_zoomable(&$variables) {
  // TODO: Remove all this and put a simply {{ attach_library('photoswipe/photoswipe.init') }}
  // into flexible_image.html.twig to initialize photoswipe, once
  // photoswipe doesn't need a HTML5 template anymore.
  // That will be the case with Photoswipe v5!
  // for details see https://www.drupal.org/project/drowl_paragraphs/issues/3345294
  $paragraph = $variables['paragraph'];
  if ($paragraph->hasField('field_paragraphs_image_zoomable') && !$paragraph->get('field_paragraphs_image_zoomable')->isEmpty()) {
    // Attach the photoswipe library and template, if zoom is enabled:
    \Drupal::service('photoswipe.assets_manager')->attach($variables);
  }
}

And once through the photoswipe 'Load PhotoSwipe on all non-admin pages' option and adding the 'photoswipe' class to the image link in flexible_image.html.twig. Furthermore, the pswp data attributes are not compatible with Photoswipe 5 (as @thomas.frobieter pointed out).

data-size="1280x397" (old) vs. data-pswp-width="1280" / data-pswp-height="618" (new)

Ok, all done, should work with photoswipe 5 now. We need to make sure to disable the global photoswipe option once enabled.

@thomas.frobieter releasing this will force us to upgrade all pages using drowl_paragraphs 4.x to use Photoswipe 5. From my perspective that's okay and better than having one additional branch. Do you agree?

All resolved, please review! Once again.

Looks good to me! I'll create a new release.

Automatically closed - issue fixed for 2 weeks with no activity.