change documentation of WindowMainStateListener

Co-authored-by: Reuben Turner <[email protected]>

lib/src/utils.dart

@@ -91,8 +91,11 @@ class MacOSBrightnessOverrideHandler {
   }
 }
 
-/// A class that listens for changes to the application's window being the main
-/// window, and notifies listeners.
+/// A class that listens for changes to the application's main window. 
+///
+/// A common use-case for responding to such changes would be to mute the colors of certain
+/// primary UI elements when the window is no longer in focus, which is something native
+/// macOS applications do out of the box.
 class WindowMainStateListener {
   /// A shared instance of [WindowMainStateListener].
   static final instance = WindowMainStateListener();