add aria-required to caniuse, if not already there

[leonsegal]

Hi

I may be being dumb, but I could not find aria-required, e.g to indicate a group of elements in a fieldset are all required:

<fieldset role="group" aria-required="true">
    ...
</fieldset>

Thanks
Leon

[cvrebert]

Subfeature of http://caniuse.com/#feat=wai-aria