Add domainIncludes RsvpAction to comment property

[danbri]

http://schema.org/RsvpAction

It has been suggested that RsvpAction descriptions would benefit from having ability to associate a comment.

See also a similiar point in #300 and ReplyAction and Answer from @vholland

[danbri]

In the spirit of re-using rather than duplicating our existing noun-oriented types, I think we should do this. Queueing an implementation for sdo-gozer. I'm also modernizing its range to permit Comment type as a value (long overdue). Definitions would then be:

<div typeof="rdf:Property" resource="http://schema.org/comment">
  <span class="h" property="rdfs:label">comment</span>
  <span property="rdfs:comment">Comments, typically from users, on this CreativeWork.</span>
  <span>Domain: <a property="http://schema.org/domainIncludes" href="http://schema.org/CreativeWork">CreativeWork</a></span>
  <span>Domain: <a property="http://schema.org/domainIncludes" href="http://schema.org/RsvpAction">RsvpAction</a></span>
  <span>Range: <a property="http://schema.org/rangeIncludes" href="http://schema.org/UserComments">UserComments</a></span>
  <span>Range: <a property="http://schema.org/rangeIncludes" href="http://schema.org/Comment">Comment</a></span>
</div>

[danbri]

Per discussion on the commit, one final change:

• "Comments, typically from users, on this CreativeWork." becomes "Comments, typically from users."