title: How to freeze the screen when popover is displayed in browser?
body: <p>I would like to realize a simple tutorial to explain the role of the specific areas of my website realised with popovers.
  My idea is that when user clicks on the button <code>start tutorial</code>, then some popovers are displayed in sequence on different elements, and when a popover is open, the rest of the screen is blocked and the user can only press <code>next</code> to close the current popover and open the following one, until the tutorial is concluded.
  How can i do that?</p>