Easy diff to document in code how to enable logging of Shadow Tree instrospection

Summary:
Easy diff to document in code how to enable logging of Shadow Tree instrospection

changeLog: [Internal] Internal change used on Fabric

Reviewed By: JoshuaGross

Differential Revision: D21150196

fbshipit-source-id: 8eb23ec3ea1d574b79b09333428ab52c851065dd

ReactCommon/fabric/debug/DebugStringConvertible.h

@@ -26,6 +26,9 @@ namespace react {
 // Additional logging can be enabled editing yoga.cpp (e.g. gPrintChanges,
 // gPrintSkips)
 
+// To Debug introspection of RN Shadow tree, uncomment the following line:
+// #define RN_SHADOW_TREE_INTROSPECTION 1
+
 #if RN_DEBUG_STRING_CONVERTIBLE
 
 class DebugStringConvertible;