Check out color.io for reference. It is a color grading focused app but nevertheless has bells and whistles for many workflows regarding raw photos. The thing is that it is offline, runs on browser, and is much faster than Rawtherapee or Darktable on my aging PC.
It’s not "web" in a way you mean that, it uses rust and gpu processing very heavily, up to the point where it just launched by web browser and that’s it