[AriaNotify] Braille Support

[alisonmaher]

As discussed in https://github.com/w3c/aria/discussions/1958#discussioncomment-6200866, there may be cases where an author would want to provide a separate notification string for braille users. @cookiecrook noted that if so, it should align with aria-braille* attributes.

I think this is a great idea, and I could imagine use cases where an author would want to provide different strings for braille. However, I would like to propose that we consider this for a future version of the API instead to allow us to gather feedback from developers and end users as ariaNotify starts to get adopted with its current set of functionality. This will help inform the best way to incorporate this additional customizability going forward.