title: How to add jstree via webpacker to Rails
body: <p>I have a Rails 6 app where I added <code>jstree</code> library via yarn. I have <code>application.js</code> file where are the <code>require</code> statement. I want to do the following
  <code>$('#tree').jstree();</code> but this results in <code>function jstree undefined</code> exception. How should I require it?</p>