Add compatibility test issue template

.github/ISSUE_TEMPLATE/compatibility_test.md

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+---
+name: Indexer-Dashboard compatibility testing with OpenSearch
+about: Issue to perform internal testing of Indexer-Dashboard packages under a new version of OpenSearch
+title: 'Indexer-Dashboard testing under OpenSearch (version)'
+labels: request/operational, level/task, type/test
+assignees: ''
+
+---
+
+
+## Description
+
+We need to ensure our components work under the new version of OpenSearch. The goal of this issue is to test our packages, their lifecycle and the main correct communication of Indexer and Dashboard.
+
+For that, we need to:
+
+- [x] (Prerequisite) \<indexer-opensearch-compatibility-issue> 
+- [x] (Prerequisite) \<dashboard-opensearch-compatibility-issue>
+- [ ] Verify the packages installs
+- [ ] Verify the package upgrades: \<from-version> ⇾ \<to-version>
+- [ ] Indexer-Dashboard communication works
+
+
+Tests must be performed following the official documentation under RHEL 9 and Ubuntu 22.04 operating systems, or newer versions if available and supported.
+
+## Issues
+-  _List here the detected issues_