Update Metadata names

I've just got the following error:

Bad value twitter:domain for attribute name on element meta: Keyword
> twitter:domain is not registered.
> Syntax of metadata name:
> A metadata name listed in the HTML specification or listed in the WHATWG
> wiki.


But when you look at the WHATWG wiki, you can see that it's there for quite
a while now:
http://wiki.whatwg.org/index.php?title=MetaExtensions&oldid=8958 (2
February 2013)

Could you please add this to the validator?

Best regards,
Martin