title: How to configure Ransack Rails Gem to add NULLS LAST to sort
body: <p>I would like Ransack to always add <code>NULLS LAST</code> which will put nulls last for the sort column.</p>
  
  <p>Any way to do this?</p>
  
  <p>I opened a github issue on this one: <a href="https://github.com/activerecord-hackery/ransack/issues/443" rel="nofollow">https://github.com/activerecord-hackery/ransack/issues/443</a></p>