add tags to tshowcase

add_action( 'init', 'tshowcase_add_tags' );
function tshowcase_add_tags() {
    register_taxonomy(
        'top-month',
        'tshowcase',
        array(
            'label' => __( 'Top of the Month' ),
            'rewrite' => array( 'slug' => 'top-month' ),
            'hierarchical' => false,
        )
    );
}