Scripts in this directory are of no interest for end users. They are part of internal tooling to automate building of the gRPC C# package for Unity.
unitypackage_skeleton - preconfigured .meta files for the unity package layout. The actual assemblies and native libraries will be added into this hierarchy while building the package. Note: The .meta file were created by the Unity IDE by manually adding the assemblies/native libraries to a Unity project and configuring their target plaform/architecture in the UI (these setting get recorded in .meta files). The .meta format is not very well documented and there seems to be no easy way to generate them automatically.