docs: reference testing guide in data mode docs

Author: ryanflorence

docs/start/data/testing.md

@@ -0,0 +1,8 @@
+---
+title: Testing
+order: 9
+---
+
+# Testing
+
+You can use `createRoutesStub` in data and framework modes. Please refer to the [Testing Guide](../framework/testing.md).

docs/start/framework/testing.md

@@ -5,7 +5,7 @@ order: 9
 
 # Testing
 
-[MODES: framework]
+[MODES: framework, data]
 
 ## Introduction