Add isArray in devTools utils (#22438)

packages/react-devtools-shared/src/isArray.js

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+const isArray = Array.isArray;
+
+export default isArray;