Add Feedly featured image class "webfeedsFeaturedVisual" to featured images in Wordpress
If you are looking to add a class to your featured image:
Edit the reference to call the featured image in your template:
<?php the_post_thumbnail('post-thumbnail', array( 'class' => "zoomer-class attachment-post-thumbnail")); ?>
Change zoomer-class
to your own class name.
More info here:https://wordpress.org/support/topic/featured-image-add-image-class?replies=4
Hope it helps!