Imports Markdown from a remote site (like GitHub) into WordPress as pages.

Each importer needs to override the abstract methods:

• get_base() - Base URL for imported pages. This will be stripped from the key before comparing.
• get_manifest_url() - URL pointing to the manifest.
• get_post_type() - Post type to import as.

The manifest should be a JSON object, with the keys set to the desired permalink (excluding the base path). Each item should also be a JSON object, containing the following keys:

• slug - Post name to insert. (Must match the final path-part of the key.)
• markdown_source - URL for the Markdown file to parse into content.
• parent - Key for the parent to store under. (Must correspond to the non-final path-parts of the key.)
• title - Title to use when creating post. Used temporarily, will be updated from the Markdown file. If not specified, defaults to slug (but will be updated from Markdown source).

Note: The Handbook index should have the slug index.

Example:

{
	"foo": {
		"title": "Temporary Foo Title",
		"slug": "foo",
		"markdown_source": "https://raw.githubusercontent.com/WordPress/doc-repo/master/foo.md",
		"parent": null
	},
	"foo/bar": {
		"title": "Temporary Bar Title",
		"slug": "bar",
		"markdown_source": "https://raw.githubusercontent.com/WordPress/doc-repo/master/foo/bar.md",
		"parent": "foo"
	},
	"foo/bar/quux": {
		"title": "Temporary Quux Title",
		"slug": "quux",
		"markdown_source": "https://raw.githubusercontent.com/WordPress/doc-repo/master/foo/bar/quux.md",
		"parent": "foo/bar"
	}
}