Add a 'skip to search' link to the top of a WordPress theme.

skip-to-search.php

<?php
/**
 * Plugin Name: Skip to search.
 * Plugin URI: https://prothemedesign.com
 * Description: Add "Skip to search" button to site header.
 * Author: Ben Gillbanks
 * Version: 1.0
 * Author URI: https://prothemedesign.com
 * Text Domain: sts
 */


function sts_footer() {

?>
<script>
	(function( $ ) {
		// Find search widget id.
		var $search = $( '.search-form:first' );

		if ( $search.length < 1 ) {
			return;
		}

		$search.parent( '.widget-wrap' ).attr( 'id', 'skip-to-search' );

		var skip_link = $( '<a href="#skip-to-search" class="screen-reader-shortcut"><?php esc_html_e( 'Skip to Search', 'sts' ); ?></a>' );

		$( 'a.screen-reader-shortcut[href="#site-content"]' ).after( skip_link );

	})( jQuery );
</script>
<?php

}

add_action( 'wp_footer', 'sts_footer' );