exclude json serialization example macro from analysis

Author: jakemac53

analysis_options.yaml

@@ -5,4 +5,5 @@ analyzer:
     - working/macros/example/lib/auto_dispose.dart
     - working/macros/example/lib/data_class.dart
     - working/macros/example/lib/observable.dart
+    - working/macros/example/lib/json_serializable.dart
     - working/macros/example/bin/user_main.dart