Feature request: API to add scrollable DOM elements as overlays

[thesoftwarephilosopher]

I'd like to e.g. add a DOM element somewhere (like an <img>) so that whenever the user scrolls the terminal, the element will scroll as if it's also part of the terminal character grid (even though it's just a DOM element). An API to add a DOM element to the scrollable terminal DOM element would allow me to do this. Or if this is already possible, this would then be a request to mention that API in the documentation. Thanks for your time in reading this request :) and great work btw.

[Tyriar]

I think this is captured in #1852, there is also some image support @jerch was looking into which is tracked in #614