Add docs for GA tracking

docs/configuration.md

@@ -5,8 +5,22 @@ nav_order: 2
 ---
 
 # Configuration
+{: .no_toc }
 
-Just the Docs has some specific configuration parameters that can be defined in your Jekyll site's `_config.yml` file.
+
+Just the Docs has some specific configuration parameters that can be defined in your Jekyll site's _config.yml file.
+{: .fs-6 .fw-300 }
+
+## Table of contents
+{: .no_toc .text-delta }
+
+1. TOC
+{:toc}
+
+---
+
+
+View this site's [_config.yml](https://github.com/pmarsceill/just-the-docs/tree/master/_config.yml) file as an example.
 
 ## Search enabled
 
@@ -48,3 +62,11 @@ addEvent(toggleDarkMode, 'click', function(){
 </script>
 
 See [Customization]({{ site.baseurl }}{% link docs/customization.md %}) for more information.
+
+## Google Analytics
+
+```yaml
+# Google Analytics Tracking (optional)
+# e.g, UA-1234567-89
+ga_tracking: UA-5555555-55
+```