Make Engine implement IDisposable (#1153)

Jint/Engine.cs

@@ -23,7 +23,7 @@ using Jint.Runtime.References;
 
 namespace Jint
 {
-    public partial class Engine
+    public sealed partial class Engine : IDisposable
     {
         private static readonly ParserOptions DefaultParserOptions = new("<anonymous>")
         {
@@ -1356,5 +1356,10 @@ namespace Jint
 
             return result;
         }
+
+        public void Dispose()
+        {
+            // no-op for now
+        }
     }
 }