Slick JS A11y `listbox`, `aria-selected`, `aria-describedby`, add `role="option"

slickjs-a11y-fixes.js

/* a11y fixes */
  // a11y fixes: init
  var $slickSlide = $('.slick-slide');

  // a11y fixes: set aria attributes
  $slickSlide
    .attr('role', 'option')
    .attr('aria-selected', 'false')
    .removeAttr('aria-describedby');

  // a11y fixes: set current 'aria-selected' to 'true'
  $('.slick-current').attr('aria-selected', 'true');
  
  // a11y fixes: generic label
  $('.slick-track').attr('aria-label', 'carousel');

  // a11y fixes: on after slide change
  $('.slick').on('afterChange', function(event, slick, currentSlide, nextSlide){
    $slickSlide.attr('aria-selected', 'false');
    setTimeout(function(){ $slickSlide.removeAttr('aria-describedby'); }, 0);
    $('.slick-current').attr('aria-selected', 'true');
  });