[REEF-1803] Fix build break in master for not follow RAT rule
Fix missing license header in NuGet.config
JIRA:
[REEF-1803](https://issues.apache.org/jira/browse/REEF-1803)
Pull Request
This closes #1309
diff --git a/lang/cs/nuget.config b/lang/cs/nuget.config
index 771b00e..ddd79f7 100644
--- a/lang/cs/nuget.config
+++ b/lang/cs/nuget.config
@@ -1,4 +1,22 @@
<?xml version="1.0" encoding="utf-8"?>
+<!--
+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.
+-->
<configuration>
<packageSources>
<add key="dotnet" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" />