Add a security policy (#3456)

Co-authored-by: Valeriu Predoi <[email protected]>

SECURITY.md

@@ -0,0 +1,14 @@
+# Security Policy
+
+## Supported Versions
+
+Only the [latest version][latest] of ESMValTool is currently being supported
+with security updates.
+
+## Reporting a Vulnerability
+
+If you find a vulnerability, please contact the
+[ESMValTool Tech Lead Team][TLT].
+
+[latest]: https://github.com/ESMValGroup/ESMValTool/releases
+[TLT]: mailto:[email protected]