Create a security policy (#1879)

## Description

This helps with meeting community standards too.

## Does this PR need a docs update or release note?

- [x] ⛔ No 

## Type of change

- [x] 🗺️ Documentation

SECURITY.md

@@ -0,0 +1,7 @@
+# Security Policy
+
+## Reporting a Vulnerability
+
+If you find a security vulnerability, please do not file a public GitHub
+issue. Please report this to security@corsobackup.io. In most cases, we
+will respond within 48 hours or less.