Adds FILR documents to the WordPress search.

functions.php

<?php

/**
 * Adds FILR documents to the WordPress search.
 *
 * @param  object $query current query.
 * @return object
 */
function add_filr_to_search( $query ) {
	if ( $query->is_search ) {
		$query->set( 'post_type', array( 'post', 'page', 'filr' ) );
	}

	return $query;
}
add_filter( 'pre_get_posts', 'add_filr_to_search' );