CAAS-3775: SECURITY.md

[marynicholson3]

Jira

Adds .MD file as required by redlines.

Checklist

• Ensure your branch name matches one of the patterns that will trigger the CI checks (feature/** or bugfix/**).
• Brief description of work completed, and any technical decisions made as part of the PR
• PR link added as a comment to the relevant JIRA ticket
• PR Labels have been applied to the Pull Request
• Reviewers have been assigned (only if specific named reviewers are necessary)
• PR link shared on Slack and Teams
• 2 reviews received

[marynicholson3]

Closed - merged as part of Gabriel's package change