Add screen reader label to post navigation

Hello,

Could you please add a screen reader label to post navigation links?

if ( ! function_exists( 'storefront_post_nav' ) ) {
	/**
	 * Display navigation to next/previous post when applicable.
	 */
	function storefront_post_nav() {
		$args = array(
			'next_text' => '<span class="screen-reader-text">Next post: </span>%title',
			'prev_text' => '<span class="screen-reader-text">Previous post: </span>%title',
			);
		the_post_navigation( $args );
	}
}

Thanks.