Add MF2 site health check

[dshanske]

https://make.wordpress.org/core/2019/04/25/site-health-check-in-5-2/

This would require php-mf2 and WordPress 5.2 but it would allow for checks on someone's site for markup.

[tw2113]

What are you thinking for this one? Some cached HTTP requests that parse the latest single post or some other URL and compile results of MF2 attributes?

[dshanske]

Thinking indiewebify.me as a site health tool. It looks at your page by polling the HTML when the check is run and tells you if you have an h-card, h-feed, h-entry, etc