title: Add "you might be interested in" products to transactional emails in magento
body: <p>For example if one user orders x product. it would be nice that he gets an email with the confirmation, and below the order details something like</p>
  
  <p>You might be interested in:
  Then, show the related products/upsells/cross sells.</p>
  
  <p>Is this even possible?
  I do know HTML, but I don't know PHP in detail.</p>
  
  <p>I am interested in full code to write this transactional email, do not worry for design details, but for the functional details.</p>