Add react-dom to externals

Author: Aljullu

webpack.config.js

@@ -28,6 +28,7 @@ module.exports = {
     ]
   },
   externals: {
-    'react': 'commonjs react'
+    'react': 'commonjs react',
+    'react-dom': 'commonjs react-dom',
   }
 };