improve readme

quad/doc/Unity_notes.md

 # Unity Notes
 
 - When using Unity, be sure to define `UNITY_INCLUDE_CONFIG_H`
-to use the [`unity_config.h`](/Unity/src/unity_config.h).
-  - For the quad directory, this is done at compile-time of the Unity library [here](/Unity/src/Makefile#L4)
-and at compile-time of the test runner [here](/quad/library.mk#L58).
+to use the [`unity_config.h`](/Unity/src/unity_config.h). (Details on why are in the
+[Unity Configuration Guide](/Unity/doc/UnityConfigurationGuide.md).)
+  - For the quad directory, this is done at compile-time of the Unity library [_here_](/Unity/src/Makefile#L4)
+and at compile-time of the test runner [_here_](/quad/library.mk#L58). Both rely on the flag defined
+[_here_](/quad/library.mk#L19).
 - Follow the examples in the [`Unity/examples`](/Unity/examples) for a guide, as well
 as the documentation in [`Unity/docs`](/Unity/docs)
   - The [Unity Getting Started guide](/Unity/doc/UnityGettingStartedGuide.md) and the