Enable Google Analytics (#11)

* Enable Google Analytics

* Use variable for tag

Author: willeastcott

_config.yml

@@ -26,6 +26,7 @@ baseurl: "" # the subpath of your site, e.g. /blog
 url: "https://blog.playcanvas.com/" # the base hostname & protocol for your site, e.g. http://example.com
 twitter_username: playcanvas
 github_username:  playcanvas
+google_analytics: G-NDG04ENSGD
 
 # Build settings
 theme: minima

_includes/google-analytics.html

@@ -0,0 +1,9 @@
+<!-- Google tag (gtag.js) -->
+<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>