Add TypeScript declarations

javascript/sources/sync.d.ts

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+ import type {Yoga} from './wrapAsm';
+
+ export * from './YGEnums';
+ export * from './wrapAsm';
+
+ declare const yoga: Yoga;
+ export default yoga;