I've thought about it, but the ability to just airplay from my mac or my ipad to the tv kinda reduces the need.
The subfire 4 core library should provide a head start for the javascript API side (with typescript types, btw), though i've not gone out of my way to document them yet as my priority has been on rebuilding the UI on top of them.
https://www.npmjs.com/package/@subfire/core This library is independent of all of the UI-specific features of subfire. There is also @subfire/hooks which provides react hooks for common functionality from core without any specific UI elements, and then the WIP layer of @subfire/components which are all built on MUI-5.