Add a Supported Versions table to SECURITY.md

Add a section to the security policy that describes the support status of each release, like the [OIIO table](https://github.com/AcademySoftwareFoundation/OpenImageIO/security#supported-versions).

Start by reading SECURITY.md and compare the linked OpenImageIO security page's Supported Versions table for structure. Add a supported-versions section covering each OpenCue release and its support status; done means the policy clearly presents those release statuses in a table.

Written by the indexing model from the issue text.