Create ISSUE_TEMPLATE.md (apache#608)

* Create ISSUE_TEMPLATE.md

* add dev mailing list and jira links

.github/ISSUE_TEMPLATE.md

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+## Before you submit an issue
+The Kubernetes scheduler backend is currently being upstreamed to the main [Apache Spark project](https://github.com/apache/spark).
+We are attempting to re-direct as much new development as possible to the upstream.
+Please consider whether your issue can be submitted against the Apache Spark project,
+and submit there as an Apache Spark JRIA, if possible.
+
+If you have any questions about whether an issue should be submitted upstream or against this fork,
+please feel free to reach out on the following channels:
+
+* Apache Spark developer mailing list: dev@spark.apache.org
+* Apache Spark [JIRA](https://issues.apache.org/jira/)
+* Big Data SIG [slack channel](https://kubernetes.slack.com/)
+* Regular Big Data SIG [meetings](https://github.com/kubernetes/community/tree/master/sig-big-data)