adding necessary copyright etc

Author: Igor Altsybeev

Detectors/Upgrades/ALICE3/TRK/macros/test/CheckClusterSizeVsEta.C

@@ -1,3 +1,17 @@
+// Copyright 2019-2026 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+/// \file CheckClusterSizeVsEta.C
+/// \brief A post-processing macro to draw average cluster size vs eta
+
 #include <TCanvas.h>
 #include <TFile.h>
 #include <TH1F.h>