title: Create a custom titlebar for NSWindow
body: <p>I would like to achieve something like the following: keep the quit and minimize buttons but blend my app's title bar into it's contentView. I've seen examples where people hide the title bar altogether but I need the buttons to be present.</p>
  
  <p>Thanks in advance!
  CS</p>
  
  <p><img src="https://i.stack.imgur.com/z3cJK.png" alt="enter image description here"></p>