By default Pinot loads all the plugins, so you can just drop this plugin there. Also, if you specify -Dplugins.include, you need to put all the plugins you want to use, e.g. pinot-json, pinot-avro , pinot-kafka-2.0...
GCP filesystems provides the following options -
projectId - The name of the Google Cloud Platform project under which you have created your storage bucket.
gcpKey - Location of the json file containing GCP keys. You can refer to download the keys.
Each of these properties should be prefixed by pinot.[node].storage.factory.class.gs. where node is either controller or server depending on the config