misc: update googleAnalytics

Author: ertuil

layouts/partials/head.html

@@ -21,15 +21,7 @@
         <link href="{{ .RelPermalink }}" rel="feed" type="{{ .MediaType.Type }}" title="{{ $.Site.Title }}" />
     {{ end }}
 
-    {{ if .Site.Config.Services.GoogleAnalytics.ID }}
-        <script async src="https://www.googletagmanager.com/gtag/js?id={{ .Site.Config.Services.GoogleAnalytics.ID }}"></script>
-        <script>
-          window.dataLayer = window.dataLayer || [];
-          function gtag(){dataLayer.push(arguments)};
-          gtag('js', new Date());
-          gtag('config', '{{ .Site.Config.Services.GoogleAnalytics.ID }}');
-        </script>
-    {{ end }}
+    {{ template "_internal/google_analytics.html" . }}
 
     {{ if or .Page.Params.math .Site.Params.math }}
     <!-- adds MathJax support -->