Add image credit below image & linked to media gallery

Hi there!

We're looking to add an image credit field below the featured image (http://prntscr.com/a4j8se) (or any image inserted into a post). The credit information would need to be added directly in the media gallery (in a separate field, just as Alt, description, etc) (http://prntscr.com/a4j96g)

We've already created a child theme and copied the single.php

thanks!