Add Open SSF Best practices

README.md

@@ -4,6 +4,7 @@
 ![Build status](https://img.shields.io/travis/Dolibarr/dolibarr/develop.svg)
 [![Minimum PHP Version](https://img.shields.io/badge/php-%3E%3D%205.6-8892BF.svg?style=flat-square)](https://php.net/)
 [![GitHub release](https://img.shields.io/github/v/release/Dolibarr/dolibarr)](https://github.com/Dolibarr/dolibarr)
+[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/5521/badge)](https://bestpractices.coreinfrastructure.org/projects/5521)
 
 Dolibarr ERP & CRM is a modern software package that helps manage your organization's activity (contacts, suppliers, invoices, orders, stocks, agenda…).