Added UI for DunGenExtender

Made DevOnly fields readonly

DunGenPlus/DunGenPlusEditor/ReadOnlyPropertyDrawer.cs

@@ -0,0 +1,22 @@
+using DunGenPlus.Attributes;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using UnityEditor;
+using UnityEngine;
+using UnityEditor.UIElements;
+using UnityEngine.UIElements;
+
+namespace DunGenPlusEditor {
+  [CustomPropertyDrawer(typeof(ReadOnlyAttribute))]
+  public class ReadOnlyPropertyDrawer : PropertyDrawer {
+
+    public override VisualElement CreatePropertyGUI(SerializedProperty property) {
+      var item = new PropertyField(property);
+      item.SetEnabled(false);
+      return item;
+    }
+  }
+}