Add documentation on compatability with h-review

[capjamesg]

The h-feed wiki page is unclear on its compatibility with h-review.

In the "Properties" section, the only guidance given for children is:

nested h-entry objects representing the items of the feed

Given how a h-review could be a child of a h-feed item, I recommend that we add it to the list of children.

The use case for a h-review in a h-feed is creating a marked-up list of reviews. For instance, I am building a feed of all the coffees I consume that is marked up using mf2.

In the section on "Properties", the h-review page does say:

Several of these seem to be because of h-review convergence towards h-entry, as h-review gets used alongside h-entry within h-feed:

The wording here is somewhat unclear. Are h-reviews to be used in the same feed as a h-entry? Or as part of a h-entry? Or something else?

[dshanske]

Related #3