aria-readonly: Consider explicitly calling out UIA mapping for controls that don't follow the ValuePattern

[sivakusayan]

As discussed in w3c/aria#1309 (comment), UIA doesn't have a mapping for readonly checkboxes, even though aria-readonly is allowed on checkboxes. Readonly semantics end up being exposed through the AriaProperties property instead. Should the AAM be updated to call this out in the aria-readonly table? It seems like that is done for cases like aria-sort.

[spectranaut]

Sorry for only replying to this one as well, a year later! This is also a reasonable and useful change. Let me know if you would like to open a PR with the change, otherwise I'll put it on my to dos.