TinyMCE from a CDN (what they call 'Cloud') is not free any more but if you have a plan, you can add something like this to your custom.js file:
Code:
$(document).on('ready pjax:scriptcomplete',function(){
  $.getScript('https://cloud.tinymce.com/stable/tinymce.min.js', function(data, textStatus, jqxhr) {
    tinymce.init({
      selector: '.text-item textarea',
      menubar: false,
      setup: function (editor) {
        editor.on('change', function () {
          tinymce.triggerSave();
        });
      },
      plugins: [
        'advlist autolink lists link image charmap print preview anchor textcolor',
        'searchreplace visualblocks code fullscreen',
        'insertdatetime media table contextmenu paste code help wordcount'
      ],
      toolbar: 'insert | undo redo |  formatselect | bold italic backcolor forecolor | alignleft aligncenter alignright alignjustify | bullist numlist outdent indent | code paste removeformat | help',
      content_css: [
        '//fonts.googleapis.com/css?family=Lato:300,300i,400,400i',
        '//www.tinymce.com/css/codepen.min.css'
      ]
    });
  });
});