Add HubSpot Tracking Code (In Production Only)

Author: j28smith

marketing/layouts/partials/footer.html

@@ -65,3 +65,7 @@
     © {{site.Title}} {{ now.Year }} All Rights Reserved.
   </div>
 </footer>
+
+{{ if hugo.IsProduction }}
+  <script type="text/javascript" id="hs-script-loader" async defer src="//js-na3.hs-scripts.com/342246859.js"></script>
+{{ end }}