Add SECURITY.md to outline security practices and reporting procedures

[johncollinson2001]

Description

This update introduces a SECURITY.md file that details security practices and reporting procedures for vulnerabilities. It aims to enhance the repository's security posture by providing clear guidelines for reporting issues and general inquiries.

Type of change

Please check the relevant options:

🔲 New feature (a change which adds functionality)
🔲 Bug fix (a change which fixes an issue)
🔲 Refactoring (code cleanup or optimisation)
🔲 Testing (new tests, or improvements to existing tests)
🔲 Pipelines (changes to pipelines and workflows)
🔲 Documentation (changes to documentation)
✅ Other (something that's not listed here - please explain)

Checklist

Please check the relevant options:

✅ My code aligns with the style of this project
🔲 I have added comments in hard to understand areas
🔲 I have added tests that prove my change works
🔲 I have updated the documentation
🔲 If merging into main, I'm aware that the PR should be squash merged with a commit message that adheres to the semantic release format

Additional Information

Please provide any additional information or context related to this pull request.

[Copilot]

Pull request overview

This PR adds a SECURITY.md policy file to document how to report vulnerabilities and where to direct general security enquiries, improving the repository’s security reporting posture.

Changes:

• Added a new SECURITY.md with guidance on private vulnerability reporting via GitHub Security Advisories.
• Added a brief section for general security enquiries with a contact email address.

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