app/views/layouts/decidim/_head_extra.html.erb
<% if I18n.locale != :en %>
<%= javascript_include_tag "datepicker-locales/foundation-datepicker.#{I18n.locale}.js" %>
<% end %>
<% if Rails.env.production? %>
<!-- Global Site Tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-9035597-13"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments)};
gtag('js', new Date());
gtag('config', 'UA-9035597-13');
</script>
<% end %>