Update configuration.mdx (#212)

Author: cabljac

docs/configuration.mdx

@@ -190,6 +190,14 @@ If provided, Google Tag Manager will be added to all of your documentation pages
 | ------------------ | -------- | ------- |
 | `googleTagManager` | `string` |         |
 
+### `googleAnalytics`
+
+If provided, Google Analytics will be added to all of your documentation pages.
+
+| Key                | Type     | Default |
+| ------------------ | -------- | ------- |
+| `googleAnalytics` | `string` |         |
+
 ### `zoomImages`
 
 A boolean value representing whether images are zoomable by default.