add apache-rat for .checkstyle file

Author: xiangdong huang

.checkstyle

@@ -1,4 +1,24 @@
 <?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.
+
+-->
 
 <fileset-config file-format-version="1.2.0" simple-config="true" sync-formatter="false">
   <local-check-config name="google" location="checkstyle.xml" type="project" description="">

pom.xml

@@ -465,8 +465,6 @@
                             <exclude>licenses/*</exclude>
                             <!-- generated by Github -->
                             <exclude>.github/**</exclude>
-                            <!--Checkstyle files -->
-                            <exclude>.checkstyle</exclude>
                             <!--Generated by Apache Release -->
                             <exclude>local-snapshots-dir/**</exclude>
                             <!-- JSON can't contain comments and therefore no Apache header -->