title: Completion in NSTextView
body: <p>I am looking for a way (or code) to have a completion list close to the one of xcode 
  <img src="https://i.stack.imgur.com/r9nau.jpg" alt="xcode completion"></p>
  
  <p>Do you know how to achieve this?</p>
  
  <p>Thanks and regards,</p>