chore: update CONTRIBUTING.md licensing information (#732)

Ready for rlease.
add licensing information to the CONTRIBUTING.md file.

Author: psxjoy

CONTRIBUTING.md

@@ -1,3 +1,19 @@
+<!--
+- Licensed to the Apache Software Foundation (ASF) under one or more
+- contributor license agreements.  See the NOTICE file distributed with
+- this work for additional information regarding copyright ownership.
+- The ASF licenses this file to You 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.
+-->
 # Contribution Guidelines