title: Get index # of array in twig
body: <p>Trying to output the index # of an array in twig, having trouble finding it in the docs.  Anyone know how to get it?</p>
  
  <pre><code>array(2) {
    [0]=&gt;
    array(2) {
      ["testimonial"]=&gt;
      string(18) "Derby Heist Test 1"
      ["author"]=&gt;
      string(6) "test 1"
    }
    [1]=&gt;
    array(2) {
      ["testimonial"]=&gt;
      string(18) "Derby Heist Test 2"
      ["author"]=&gt;
      string(6) "test 2"
    }
  }
  </code></pre>
  
  <p>so I'd like to output the index numbers 0 and 1 in a for loop. Please help.</p>