chore: revise security policy and vulnerability reporting

Updated the security policy to reflect the project's current status and reporting process for vulnerabilities.

Author: electricalgorithm

SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+As of now, the project is still not in production-grade. Please use it at your own risk. It's only one person who tries to maintain it; therefore, no security policy is promised.
+
+## Reporting a Vulnerability
+
+Please create an issue on GitHub if it's not high risk in your opinion. For anything serious, contact the maintainer via appsec@gyokhan.com.