Add assets

Assets/Cainos/Third Party/Lucid Editor/Runtime/Attributes/RequiredAttribute.cs

@@ -0,0 +1,16 @@
+using System;
+using UnityEngine;
+
+namespace Cainos.LucidEditor
+{
+    [AttributeUsage(AttributeTargets.Field)]
+    public class RequiredAttribute : Attribute
+    {
+        public readonly string message = null;
+        public RequiredAttribute() { }
+        public RequiredAttribute(string message)
+        {
+            this.message = message;
+        }
+    }
+}