Create base MapBuffer class and tests

Summary: This diff creates the base classes for MapBuffer and its tests

Reviewed By: shergin

Differential Revision: D15550730

fbshipit-source-id: a5a47edebd7c3e1b8b2c3ad2006aee0f8bdb7866

ReactCommon/fabric/mapbuffer/tests/MapBufferTest.cpp

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ */
+
+#include <memory>
+
+#include <gtest/gtest.h>
+
+TEST(MapBufferTest, testSomething) {
+  // TODO
+}