chore: add security policy (#74)

SECURITY.md

@@ -0,0 +1,18 @@
+# Security Policy
+
+The RAWeb team takes the security of the RetroAchievements platform seriously. If you discover a security issue, we appreciate your help in disclosing it to us in a responsible manner.
+
+## Reporting a Vulnerability
+
+Here's how you can report a security issue:
+
+1. **Do not report security issues in GitHub issues, discussions, or on Discord.**
+2. **Send a direct on-site message.** If you believe you've found a security vulnerability, [please send an on-site message to RAdmin](https://retroachievements.org/user/RAdmin).
+
+In your report, please include:
+
+- A brief description of the issue.
+- Steps to reproduce the issue, if possible.
+- Potential impact of the issue.
+
+We will acknowledge your report within 48 hours of receiving it. We appreciate your help as we strive to keep our site as secure as possible. Thank you.