Add missing GRPC data field (#412)

* feat(grpc): add support for data field in request body

* docs: update Readme with embedmd

rpc/server.go

@@ -82,6 +82,13 @@ func (s *Server) Send(ctx context.Context, in *proto.NotificationRequest) (*prot
 		}
 	}
 
+	if in.Data != nil {
+		notification.Data = map[string]interface{}{}
+		for k, v := range in.Data.Fields {
+			notification.Data[k] = v
+		}
+	}
+
 	go gorush.SendNotification(notification)
 
 	return &proto.NotificationReply{