I mean, I wanted to start work on it, but if someone's already released/working on one then I'd just happily use those instead.

Also, the absence of a thing usually means it's not possible to have. In my mind I think it's easy to have userscript code make API posts on behalf of the user, but maybe somehow in the intricate layers of tech it's made impossible or tedious. If so, I'd like to know before I learn it the hard way.