Add Acoss to users

USERS.md

@@ -8,6 +8,7 @@ The list of organizations that have publicly shared the usage of cert-manager:
 
 | Organization | Usage | Links |
 | :--- | :--- | :--- |
+| [<img src="https://www.acoss.fr/files/Logos/logo_acoss.png" alt="Acoss" width="100"> ](https://www.acoss.fr/) | Securing ingresses | |
 | [<img src="https://static.atomist.com/logo/atomist-color-lockup-horiz-small.png" alt="Atomist" width="100"> ](https://atomist.com/) | Securing ingresses | [Kubernetes, ingress-nginx, cert-manager & external-dns](https://blog.atomist.com/kubernetes-ingress-nginx-cert-manager-external-dns/) |
 | [<img src="https://raw.githubusercontent.com/cert-manager/website/master/assets/icons/jetstack.svg" alt="Jetstack text" width="100"> ](https://jetstack.io) | Securing MySQL inside Kubernetes | [blog](https://blog.jetstack.io/blog/securing-mysql-with-cert-manager/)  |
 | [<img src="https://media.jfrog.com/wp-content/uploads/2017/12/20133032/Jfrog-Logo.svg" alt="JFrog" width="100"> ](https://jfrog.com/) | Securing ingresses |  |