[MeL/IO] Add copyright headers.

MeshLib/IO/XDMF/XdmfWriter.cpp

+/**
+ * \file
+ * \copyright
+ * Copyright (c) 2012-2022, OpenGeoSys Community (http://www.opengeosys.org)
+ *            Distributed under a Modified BSD License.
+ *              See accompanying file LICENSE.txt or
+ *              http://www.opengeosys.org/project/license
+ */
+
 #include "XdmfWriter.h"
 
 #include <fstream>
@@ -33,4 +42,4 @@ void XdmfWriter::addTimeStep(double const& time_step)
     times.push_back(time_step);
 }
 
-}  // namespace MeshLib::IO
\ No newline at end of file
+}  // namespace MeshLib::IO

MeshLib/IO/XDMF/writeXdmf.cpp

+/**
+ * \file
+ * \copyright
+ * Copyright (c) 2012-2022, OpenGeoSys Community (http://www.opengeosys.org)
+ *            Distributed under a Modified BSD License.
+ *              See accompanying file LICENSE.txt or
+ *              http://www.opengeosys.org/project/license
+ */
 
 #include "writeXdmf.h"
 
@@ -347,4 +355,4 @@ std::function<std::string(std::vector<double>)> write_xdmf(
     return xdmf_writer_fn(ogs_version, geometry, topology, constant_attributes,
                           variable_attributes);
 }
-}  // namespace MeshLib::IO
\ No newline at end of file
+}  // namespace MeshLib::IO