0.513.0.5130420 + UniqueId

Caught up with latest API changes and implemented UniqueId.

Tokens/UniqueId.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Xml;
+
+namespace RobloxFiles.Tokens
+{
+    public class UniqueId : IXmlPropertyToken
+    {
+        public string XmlPropertyToken => "UniqueId";
+
+        public bool ReadProperty(Property prop, XmlNode token)
+        {
+            string hex = token.InnerText;
+
+            if (Guid.TryParse(hex, out var guid))
+            {
+                prop.Value = guid;
+                return true;
+            }
+
+            return false;
+        }
+
+        public void WriteProperty(Property prop, XmlDocument doc, XmlNode node)
+        {
+            var guid = prop.CastValue<Guid>();
+            node.InnerText = guid.ToString("N");
+        }
+    }
+}