Adding a new custom issue template

A new custom template for new releases.

.github/ISSUE_TEMPLATE/new-release.md

@@ -0,0 +1,19 @@
+---
+name: New Release
+about: A ticket to track new release steps
+title: Release X.Y.0.0
+labels: ''
+assignees: ''
+
+---
+
+OpenSearch X.Y.0 has been released, see [release notes](https://github.com/opensearch-project/opensearch-build/blob/main/release-notes/opensearch-release-notes-X.Y.0.md).
+Official OpenSearch release ticket: https://github.com/opensearch-project/opensearch-build/issues/XXXX
+
+Checklist:
+
+- [ ] [Compatibility Matrix](https://github.com/aiven/prometheus-exporter-plugin-for-opensearch#compatibility-matrix) is updated (TODO: link to PR)
+- [ ] Release [X.Y.0.0 tag](https://github.com/aiven/prometheus-exporter-plugin-for-opensearch/releases/tag/X.Y.0.0) is present in the repo
+- [ ] Release artifacts are available and downloadable
+- [ ] [Release notes](https://github.com/aiven/prometheus-exporter-plugin-for-opensearch/releases/tag/X.Y.0.0) published
+- [ ] Forum announcement published