I think it wouldn't be that hard to implement, and it's really a useful feature especially for when you want to quickly send a page (or a double-page) to someone in a social media.
I know "save current page" exists but it's not as fast as copying and pasting in the chat. And it's probably suited to be mentioned on another suggestion but another problem the save function has is that you can't save double pages as a single image even if you're on the double page mode. For double-spreads in comics/mangas which don't have their double-spreads as a single page it'd be impossible to save them.