Add sync timeout

src/MatrixClient.cc

@@ -436,6 +436,7 @@ void MatrixClient::sync() noexcept
 	QUrlQuery query;
 	query.addQueryItem("set_presence", "online");
 	query.addQueryItem("filter", QJsonDocument(filter).toJson(QJsonDocument::Compact));
+	query.addQueryItem("timeout", "30000");
 	query.addQueryItem("access_token", token_);
 
 	if (next_batch_.isEmpty()) {