Docs guides index fix (remix-run#3737)

Author: teameh

docs/README.md

@@ -8,6 +8,7 @@
  * [Histories](guides/Histories.md)
  * [Index Routes and Links](guides/IndexRoutes.md)
 * Advanced Usage
+ * [Testing](guides/Testing.md)
  * [Dynamic Routing](guides/DynamicRouting.md)
  * [Confirming Navigation](guides/ConfirmingNavigation.md)
  * [Server Rendering](guides/ServerRendering.md)

docs/guides/README.md

@@ -1,13 +1,15 @@
 # Guides
 
-* [Route Configuration](RouteConfiguration.md)
-* [Route Matching](RouteMatching.md)
-* [Histories](Histories.md)
-* [Index Routes and Links](IndexRoutes.md)
-* [Testing](testing.md)
-* [Dynamic Routing](DynamicRouting.md)
-* [Confirming Navigation](ConfirmingNavigation.md)
-* [Server Rendering](ServerRendering.md)
-* [Component Lifecycle](ComponentLifecycle.md)
-* [Navigating Outside of Components](NavigatingOutsideOfComponents.md)
-* [Minimizing Bundle Size](MinimizingBundleSize.md)
+* Basics
+ * [Route Configuration](RouteConfiguration.md)
+ * [Route Matching](RouteMatching.md)
+ * [Histories](Histories.md)
+ * [Index Routes and Links](IndexRoutes.md)
+* Advanced Usage
+ * [Testing](Testing.md)
+ * [Dynamic Routing](DynamicRouting.md)
+ * [Confirming Navigation](ConfirmingNavigation.md)
+ * [Server Rendering](ServerRendering.md)
+ * [Component Lifecycle](ComponentLifecycle.md)
+ * [Navigating Outside of Components](NavigatingOutsideOfComponents.md)
+ * [Minimizing Bundle Size](MinimizingBundleSize.md)