title: Safari Reader font-size control like popover
body: <p>Safari has a nice popover that is used for controlling the font size. I'm talking about that one:</p>
  
  <p><img src="https://i.stack.imgur.com/ystsI.png" alt="enter image description here"></p>
  
  <p>It's pretty nice, and my question is - how to implement something exactly like this?</p>
  
  <p>Thank you!</p>