introduce security policy

SECURITY.md

@@ -0,0 +1,15 @@
+# Security Policy
+
+## Supported Versions
+
+Use this section to tell people about which versions of your project are
+currently being supported with security updates.
+
+| Version | Supported          |
+| ------- | ------------------ |
+| 5.x     | :white_check_mark: |
+
+
+## Reporting a Vulnerability
+
+Please use [github security reporting](https://github.com/SoftEtherVPN/SoftEtherVPN/security/advisories/new)