Create SECURITY.md file for AI Context (CCC)
## Problem/motivation
Need a SECURITY.md file so people know how to report security issues.
## Solution
Copy the [one from AI core](https://git.drupalcode.org/project/ai/-/blob/0463789bab1680a69523b37108cee5b04f89fff6/SECURITY.md).
## Tasks
- Update code
- Review
issue