title: Getting the loop index in an eco template
body: <p>Is it possible to get the current loop index using the eco template engine?</p>
  
  <p>For example in Jinja2 you can do</p>
  
  <pre><code>{% for var in array %}
      {{ loop.index0 }}
  {% endfor %}
  </code></pre>
  
  <p>If not is there a more idiomatic way of getting at the index?</p>