docs: add security scan badge

Author: indaco

README.md

@@ -14,9 +14,12 @@
     <a href="https://goreportcard.com/report/github.com/indaco/tempo" target="_blank">
       <img src="https://goreportcard.com/badge/github.com/indaco/tempo" alt="go report card" />
     </a>
-   <a href="https://badge.fury.io/gh/indaco%2Ftempo" target="_blank">
+    <a href="https://github.com/indaco/sley/actions/workflows/ci.yml" target="_blank">
+    <img src="https://img.shields.io/badge/security-govulncheck-green" alt="Security Scan" />
+    </a>
+    <a href="https://badge.fury.io/gh/indaco%2Ftempo" target="_blank">
     <img src="https://badge.fury.io/gh/indaco%2Ftempo.svg" alt="version" height="18" />
-   </a>
+    </a>
     <a href="https://pkg.go.dev/github.com/indaco/tempo/" target="_blank">
       <img src="https://pkg.go.dev/badge/github.com/indaco/tempo/.svg" alt="go reference" />
     </a>