Add Google analytics to github.io page

docs/_config.yml

@@ -14,6 +14,8 @@ copyright_url: "https://jetbrains.com"
 homepage: "https://jetbrains.com/mps"
 homepage_title: "JetBrains MPS"
 github-project: fisakov/mps-coderules
+# Google Analytics
+google_analytics: UA-124237176-1
 
 # Build settings
 markdown: kramdown

docs/_includes/google-analytics.html

@@ -0,0 +1,9 @@
+<!-- Global site tag (gtag.js) - Google Analytics -->
+<script async src="https://www.googletagmanager.com/gtag/js?id={{ site.google_analytics }}"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
+
+  gtag('config', '{{ site.google_analytics }}');
+</script>

docs/_includes/head.html

@@ -3,6 +3,9 @@
 <!-- Copyright (c) 2017 James King -->
 <!-- MIT License https://opensource.org/licenses/MIT -->
 {% endcomment %}
+{% if site.google_analytics and jekyll.environment == 'production' %}
+{% include google-analytics.html %}
+{% endif %}
 <meta charset="utf-8"/>
 <script defer src="https://code.getmdl.io/1.3.0/material.min.js"></script>
 <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">