[Smush Pro] Let Smush do a check for whether a particular media file is used on the site

There are a few plugins out there that check through media files to check whether a particular file is in use by the website, for example, Media Cleaner by Meow checks each media file and allows you to delete it if it thinks that the file isn’t in use by the site, this would be really useful for smush API calls as it would reduce the number of files to be smushed if it finds some images that aren’t actually in use by the site.