Add full support for requests handled by Micropub

[jeremyfelt]

The Micropub plugin for WordPress handles Micropub requests to WordPress sites.

Right now, these incoming requests are stored as posts and post_content is built from the request to contain the correct microformats. If the Post Kinds plugin is active, then it will perform some actions based on these requests so that posts are treated as replies, bookmarks, etc...

On my site, which is the primary feature driver of the Shortnotes plugin, I would like to route Micropub requests so that they are stored as the shortnote post type instead. There should probably be some awareness of the Post Kinds plugin in the rare case that both are active.

In a first iteration, I think:

• Notes, Replies, and Bookmarks should be stored as short notes.
• Micropub's rendering of this content should be removed and provided by Shortnotes.
• Rendered content should be block editor compatible.
• Rendered content should be microformat compatible.
• The block editor UI for Shortnotes should support any fields captured via Micropub.

There's probably more, but that's a good start!