Add DateTimeToJSDate

Author: nex3

js_interop/lib/js_interop.dart

@@ -2,4 +2,5 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+export 'src/dart/date_time.dart';
 export 'src/date.dart';

js_interop/lib/src/dart/date_time.dart

@@ -0,0 +1,10 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import '../date.dart';
+
+extension DateTimeToJSDate on DateTime {
+  /// Converts this to a [JSDate] that represents the same instant in time.
+  JSDate get toJS => JSDate.fromMillisecondsSinceEpoch(millisecondsSinceEpoch);
+}