Support for focal point

I fixed the issue with Warning: Declaration of Drupal\retina_images\RetinaFocalPointImageEffectBase::applyCrop(Drupal\Core\Image\ImageInterface $image) should be compatible with Drupal\focal_point\FocalPointEffectBase::applyCrop(Drupal\Core\Image\ImageInterface $image, Drupal\crop\CropInterface $crop) in include() (line 18 of modules/retina_images/src/RetinaFocalPointImageEffectBase.php).