Add column class to each of the Genesis Footer Widgets

functions.php

add_filter('genesis_footer_widget_areas', 'lunarwp\add_columns_to_footer_widgets', 10, 2);
/**
 * Add column class to each of the footer widgets
 *
 * @since  1.0.0
 * 
 * @param string $output            HTML output for the footer widgets
 * @param string $footer_widgets 
 * @return string                   Return the amended $output
 */
function add_columns_to_footer_widgets($output, $footer_widgets)
{
    //* Use one-third when you have 3 widgets; otherwise, adjust to the number of widgets you have.  
    //* For example, 2 = one-half and 4 = one-fourth.
    $output = str_replace('widget-area', 'widget-area one-third', $output);
    $output = str_replace('footer-widgets-1 widget-area one-third', 'footer-widget-1 widget-area one-third first', $output);
    return $output;
}