[skip ci] Restore tag badge

Author: Petri Autero

modules/cloud-sql/README.md

@@ -1,6 +1,7 @@
 # Cloud SQL Module
 
 [![Maintained by Gruntwork.io](https://img.shields.io/badge/maintained%20by-gruntwork.io-%235849a6.svg)](https://gruntwork.io/?ref=repo_google_cloudsql)
+[![GitHub tag (latest SemVer)](https://img.shields.io/github/tag/gruntwork-io/terraform-google-sql.svg?label=latest)](http://github.com/gruntwork-io/terraform-google-sql/releases/latest)
 ![Terraform Version](https://img.shields.io/badge/tf-%3E%3D0.12.0-blue.svg)