add scriptable object examples

add editor window example
add attribute + drawer example

EditorCustomization/Assets/Scripts/Editor/PlayerControllerEditor.cs

@@ -1,3 +1,4 @@
+using System;
 using UnityEditor;
 
 namespace Core
@@ -5,15 +6,28 @@ namespace Core
     [CustomEditor(typeof(PlayerController))]
     public class PlayerControllerEditor : Editor
     {
+        private SerializedProperty _eventBrokerProperty;
+
+        private void OnEnable()
+        {
+            _eventBrokerProperty = serializedObject.FindProperty("eventBroker");
+        }
+
         public override void OnInspectorGUI()
         {
             base.OnInspectorGUI();
             
-            // serializedObject.Update();
+            serializedObject.Update();
             //
             // // update your serialized properties
             //
             // serializedObject.ApplyModifiedProperties();
+            
+            // warning info text if the event broker is not set
+            if (!_eventBrokerProperty.objectReferenceValue)
+            {
+                EditorGUILayout.HelpBox("Event Broker Property has to be set!", MessageType.Warning);
+            }
         }
     }
 }