title: Searchkick count query
body: <p>Does Searchkick support the Count API? - <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/search-count.html" rel="nofollow noreferrer">https://www.elastic.co/guide/en/elasticsearch/reference/current/search-count.html</a></p>
  <p>Basically I am looking to do something like the following -</p>
  <p><code>Product.search(where: { category_ids: [10] }).count</code></p>
  <p>Or should I use aggregation for this? What would be the syntax for an aggregation query using Searchkick?</p>
  <p>The important thing is, I wanna do this without retrieving the documents or all the <code>_id</code>'s because the count could be in many thousands.</p>