update readme

Author: Sebastian Gumprich

README.md

@@ -44,6 +44,7 @@ Warning: This role disables root-login on the target server! Please make sure yo
 |`sftp_enabled` | false | true to enable sftp configuration|
 |`sftp_chroot_dir` | /home/%u | change default sftp chroot location|
 |`ssh_client_roaming` | false | enable experimental client roaming|
+|`sshd_moduli_minimum` | 2048 | remove Diffie-Hellman parameters smaller than the defined size to mitigate logjam|
 
 ## Example Playbook