Example Plugin for Registering Kinds(untested)

annotation-kind-register.php

<?php
/**
 * Plugin Name: Register Annotation Post Kind - Name
 * Plugin URI: https://example.com
 * Description: Register Annotation Post Kind
 * Version: None
 * Author: 
 * Author URI: 
 * Text Domain:
 * Domain Path:
 */

function annotation_register_kind() {
          register_post_kind(
                        'annotation',
                        array(
                                'singular_name'   => __( 'Annotation', 'indieweb-post-kinds' ), // Name for one instance of the kind
                                'name'            => __( 'Annotations', 'indieweb-post-kinds' ), // General name for the kind plural
                                'verb'            => __( 'Annotated', 'indieweb-post-kinds' ), // The string for the verb or action (liked this)
                                'property'        => 'annotation-of', // microformats 2 property
                                'format'          => 'bookmark', // Post Format that maps to this
                                'description'     => __( 'Purchases, gifts, found things, or objects donated to me', 'indieweb-post-kinds' ),
                                'description-url' => 'http://indieweb.org/annotation',
                                'title'           => true, // Should this kind have an explicit title
                                'show'            => true, // Show in Settings
                        )
                );
          set_post_kind_visibility( 'follow' ); // Example of how to enable a hidden kind.
}
add_action( 'init', 'annotation_register_kind' );