support for aria-braille* properties

[pkra]

The ARIA Editors' Draft proposes the aria-braillelabel and aria-brailleroledescription property, see also https://w3c.github.io/aria/#aria-braillelabel, https://w3c.github.io/aria/#aria-brailleroledescription.

These properties are on track for ARIA 1.3. Browser support includes Gecko, WebKit and Chromium. (See also the 1.3 overview issue w3c/aria#1331 for more links to various bits and pieces.)

It would be very helpful for the ARIA WG to know whether these may be supported.