SLING-9638 - Update Starter Docker image to be based on the feature model

Add post_push hook to push release tags as latest.
diff --git a/hooks/post_push b/hooks/post_push
new file mode 100755
index 0000000..63c44e2
--- /dev/null
+++ b/hooks/post_push
@@ -0,0 +1,24 @@
+#!/bin/bash -e
+
+# 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.
+
+if [[ ${DOCKER_TAG} =~ ^[0-9]+$ ]] ; then
+    echo "Detected tag build, pushing to 'latest' tag"
+    docker tag ${IMAGE_NAME} ${DOCKER_REPO}:latest
+    docker push ${DOCKER_REPO}:latest
+fi