I found How to access data / variables with JavaScript? - Platform & Builds - Unreal Engine Forums which mentions that there’s a resize callback in the Game.html.template, so you could probably look at that to see how they did it and do the same. It’s probably a little harder for blueprints than C++, but it could lead you to the answer.
Other than that, I didn’t see much at all about this, so you’re probably just trying to do something that’s too new, IMO. Nobody’s done it yet.
Having said that, it seems interesting, and I wish I had time to look into it now.