Add security policy

SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+The following versions of Kitodo.Production are currently being supported with ongoing feature development and/or security updates.
+
+| Version | Active Development       |      Security Fixes      |
+|-----| :----------------------: |:------------------------:|
+| 3.7 | :heavy_check_mark:       |    :heavy_check_mark:    |
+| 3.6 | :heavy_multiplication_x: |    :heavy_check_mark:    |
+| 3.5 | :heavy_multiplication_x: | :heavy_multiplication_x: |
+| 3.3 | :heavy_multiplication_x: | :heavy_multiplication_x: |
+| 3.2 | :heavy_multiplication_x: | :heavy_multiplication_x: |
+| 3.1 | :heavy_multiplication_x: | :heavy_multiplication_x: |
+| 3.0 | :heavy_multiplication_x: | :heavy_multiplication_x: |
+| 2.x | :heavy_multiplication_x: | :heavy_multiplication_x: |
+| 1.x | :heavy_multiplication_x: | :heavy_multiplication_x: |
+
+## Reporting a Vulnerability
+
+If you find a vulnerability please consider immediately reporting it to our [release management team](https://github.com/orgs/kitodo/teams/kitodo-production-maintainers) or by sending an [email](mailto:[email protected]).