add analytics

layouts/partials/analytics/google.html

@@ -0,0 +1,12 @@
+<script defer src="https://www.googletagmanager.com/gtag/js?id={{ site.Params.analytics.google.id }}"></script>
+<script>
+  document.addEventListener('DOMContentLoaded', () => {
+    window.dataLayer = window.dataLayer || [];
+    function gtag() {
+      dataLayer.push(arguments);
+    }
+
+    gtag('js', new Date());
+    gtag('config', '{{ site.Params.analytics.google.id }}');
+  });
+</script>