Add contact information to security policy

[p-]

Hey 👋

I would like to report potential vulnerabilities in RAGFlow. But the current security policy is missing a security contact (e.g. email address). - So it doesn't seem possible to report vulnerabilities in private.

Instead of providing a security contact you can also enable private vulnerability reporting: https://docs.github.com/en/code-security/security-advisories/repository-security-advisories/configuring-private-vulnerability-reporting-for-a-repository for your repositories.

Thanks

[KevinHuSh]

Appreciate! Private vulnerability reporting is enabled.

[p-]

Thanks!