This pull request seeks to implement a new ifPostTypeSupports higher-order component which serves in place of the existing PostTypeSupportCheck and attempts to explore a new generalized pattern for conditional component rendering.

Example Before:

function MyFeaturedImage() {
	return (
		<PostTypeSupportCheck supportKeys="thumbnail">
			<img />
		</PostTypeSupportCheck>
	);
}

export default connect( /* ... */ )( MyFeaturedImage );

Example After:

function MyFeaturedImage() {
	return <img />;
}

export default compose( [
	ifPostTypeSupports( 'thumbnail' ),
	connect( /* ... */ ),
] )( MyFeaturedImage );

Implementation notes:

The thinking behind the naming convention is that we could create higher-order component-libraries with the following expectations:

Testing instructions:

Verify that there are no regressions in the behavior of post-type-conditional elements:

• Discussion (comments or trackbacks supports)
• Featured image (thumbnail support)
• Excerpt (excerpt support)
• Post format (post-formats support)
• Author (author support)
• Order (page-attributes support)
• Last Revision (revisions support)