Add copyright to MAINTAINERS (#2934)

* Add copyright to MAINTAINERS

* Update MAINTAINERS.md

---------

Co-authored-by: Nikolay Petrov <nikolay.a.petrov@intel.com>

MAINTAINERS.md

@@ -1,3 +1,20 @@
+<!--
+******************************************************************************
+* Copyright contributors to the oneDAL project
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*******************************************************************************/-->
+
 # Introduction
 
 This document defines roles in oneDAL project.