title: Insert UITabBarItem at Specific Index
body: <p>My <strong>Swift 4</strong> <code>UITabBarController</code> usually has <em>four</em> <code>UITabBarItem</code> items on it.
  In certain circumstances it can have <em>five</em> instead of four, but I always want the far right button to be the same. That means I need to dynamically insert and/or remove the <code>UITabBarItem</code> in the fourth "slot".</p>
  
  <p>I'm able to handle adding and removing the <code>UITabBarItem</code> in code with no problem, but I haven't been able to determine how to do it other than by using <code>.append</code>, which only will add it to the fifth "slot".</p>
  
  <p>Hours of poring over the Apple documentation and Stack Overflow have yielded no solution. How can I insert a <code>UITabBarItem</code> at a specific index?</p>