add licence header for proxy
+<!--
+ ~ Copyright (c) 2019, WSO2 Inc. (http://wso2.com) All Rights Reserved.
+ ~
+ ~ WSO2 Inc. 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.
+-->
<proxy xmlns="http://ws.apache.org/ns/synapse"
name="Sample451Proxy"
transports="https http"
