I had an idea for a plug-in to add features like this a while back. I stumbled upon a roadblock, though, during the research phase.
For such a plug-in to exist, third-party developers must be able to look up a post’s unique identifier. And that’s not possible right now. At least not in a reasonable way.
Should @manton make the post identifiers (and the blog identifier) available as Hugo parameters, such a plug-in could be created relatively easily.