Feature Request - Retain comments/licenses in merged service provider files

[vinnybod]

I am using jarjar-abrams via bazel_jar_jar.

I'd like to have the option to retain the comments in the merged service provider files. Right now, jarjar-abrams converts the comments to empty lines.

This is a comparison of a shaded jar output from jarjar-abrams (via Bazel) vs shadow (via Gradle)

--- bazel-out/k8-fastbuild/bin/clients/clients-export-compare-jar/bazel/META-INF/services/org.apache.kafka.common.config.provider.ConfigProvider
+++ bazel-out/k8-fastbuild/bin/clients/clients-export-compare-jar/gradle/META-INF/services/org.apache.kafka.common.config.provider.ConfigProvider
@@ -1,17 +1,17 @@
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+ # 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.

 org.apache.kafka.common.config.provider.FileConfigProvider
 org.apache.kafka.common.config.provider.DirectoryConfigProvider