title: How to align two Gtk3 Entry fields
body: <p>I've got a GUI that uses a GtkEntry widget to get some users input. Here's what it looks like:</p>
  
  <p><img src="https://i.stack.imgur.com/cnZTq.png" alt="enter image description here">\</p>
  
  <p>I've got it working like I want, other than the fact that the <strong>To:</strong> and <strong>CC:</strong> fields aren't aligned and that's <em>really</em> annoying.</p>
  
  <p>Is there any way I can align them with each-other so they line up perfectly? </p>