Revise security policy for clarity and updates

Updated the security policy to clarify supported versions and reporting process.

Author: nnhthuan

SECURITY.md

@@ -0,0 +1,21 @@
+# Security Policy
+
+## Supported Versions
+
+We only support the latest version of the Docker image. If you find a security vulnerability, please upgrade to the latest image first to see if it has been resolved.
+
+| Version | Supported          |
+| ------- | ------------------ |
+| latest  | ✅ |
+| < latest| ❌                |
+
+## Reporting a Vulnerability
+
+If you discover a security vulnerability within this project, please report it by [opening a new issue](https://github.com/Simplatex/android-lightweight/issues/new) on GitHub.
+
+We will acknowledge your report and provide an estimated timeline for a fix. Once a vulnerability is reported, we will:
+
+1.  Investigate and confirm the vulnerability.
+2.  Work on a fix.
+3.  Release a new version of the Docker image with the fix.
+4.  Update the issue once the fix is deployed.