Add docs to new config variable

protocol-grpc/src/main/scala/com/devsisters/shardcake/GrpcConfig.scala

@@ -11,6 +11,7 @@ import java.util.concurrent.Executor
  * @param maxInboundMessageSize the maximum message size allowed to be received by the grpc client
  * @param executor a custom executor to pass to grpc-java when creating gRPC clients and servers
  * @param shutdownTimeout the timeout to wait for the gRPC server to shutdown before forcefully shutting it down
+ * @param interceptors the interceptors to be used by the gRPC client, e.g for adding tracing or logging
  */
 case class GrpcConfig(
   maxInboundMessageSize: Int,