title: How to trigger documentation popup in vscode
body: <p>How to trigger a popup with documentation for identifier under the cursor? 
  Normally it appears when hovering the identifier using the mouse pointer:
  <a href="https://i.stack.imgur.com/x10B7.png" rel="noreferrer"><img src="https://i.stack.imgur.com/x10B7.png" alt="enter image description here"></a></p>
  
  <p>I would like to achieve this effect using a command or keyboard shortcut.</p>
  
  <p>The only related commands I found are: <code>trigger completion</code> (which doesn't show the function doc) and <code>trigger parameters hint</code> (which only works when the cursor is inside function call - parameters list). </p>