title: Rotate marker based on driving direction
body: <p>I have a marker in my Google Maps map that looks like this:</p>
  
  <p><img src="https://i.stack.imgur.com/l7N1w.png" alt="pic"></p>
  
  <p>When the user is driving, I want to rotate it based on his driving direction. How can I achieve this? I should probably use previous location and current location coords for calculation, but I have no idea how.</p>