docs: add security policy

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: vprelovac

SECURITY.md

@@ -0,0 +1,14 @@
+# Security Policy
+
+## Supported Versions
+
+| Version | Supported |
+| ------- | --------- |
+| 0.6.x   | Yes       |
+| < 0.6   | No        |
+
+## Reporting a Vulnerability
+
+Please report security vulnerabilities through [GitHub Security Advisories](https://github.com/kagisearch/fastfeedparser/security/advisories/new).
+
+You can expect an initial response within 48 hours. If the vulnerability is accepted, a fix will typically be released within a week.