Proposed: u-like attribute

[capjamesg]

Similar to the u-repost attribute described in #30, the u-like attribute is used on a post to indicate the linked resource is a like of the page on which it appears. This markup would let consumers distinguish likes on a page from other social reactions on a page using a standard. A u-like attribute may appear in a responses list or a facepile.

@dshanske noted that he publishes u-like on his website.

Note: The u-like attribute is distinct from u-like-of. u-like-of indicates the current post is a like of the linked resource, whereas u-like states the linked resource is a like of the current post.

[gRegorLove]

See also #20