Images styles should be converted to WebP

You'll be able to do this once ✨ Alter hook to adjust image effect RTBC lands, or you can start using the patch now:

/**
 * Implements hook_easy_responsive_images_image_style_alter().
 */
function my_module_easy_responsive_images_image_style_alter(ImageStyleInterface $entity): void {
  foreach ($entity->getEffects() as $effect) {
    if ($effect->getPluginId() === 'image_convert') {
      return;
    }
  }

  $entity->addImageEffect([
    'id' => 'image_convert',
    'data' => [
      'extension' => 'webp',
    ],
  ]);
}

Perhaps I'm missing something but a default pipeline using ImageAPI Optimize and a processor like ImageAPI Optimize AVIF WebP → takes care of this.

ImageAPI Optimize introduces an overhead and is very much overkill if all you want to do is convert images to Webp, because this is supported by core image styles.