Update README

Change-Id: I7b0add0b78ca04a5f9480ee04508174c80b769b1

Author: chkuang-g

README.md

@@ -172,7 +172,8 @@ package:
       you add the `-gvh_disable` option.
    1. Export your plugin by [running Unity from the command line](https://docs.unity3d.com/Manual/CommandLineArguments.html), ensuring that
       you:
-      - Include the contents of the `Assets/PlayServicesResolver` directory.
+      - Include the contents of the `Assets/PlayServicesResolver` and
+        `Assets/ExternalDependencyManager` directory.
       - Add the `-gvh_disable` option.
 
 You **must** specify the `-gvh_disable` option in order for the Version