title: How to add small red dot in UITabBarItem
body: <p>How to add red dot on the top right side of the <code>UITabBarItem</code>.
  <img src="https://i.stack.imgur.com/86IJ1.png" alt="enter image description here"></p>
  
  <p>I have searched a while and some guys said this can be done setting Badge Value of the <code>UITabBarItem</code>.But when I give it a try and  set badge value to empty space " ",the red dot is somewhat big.How can I get a proper one?Big thanks.</p>
  
  <p><img src="https://i.stack.imgur.com/H4IdQ.png" alt="enter image description here"></p>