Create a feature for TLS self-test

[freephile]

https://github.com/drwetter/testssl.sh is cloned, then invoked by src/scripts/ssl-selftest.sh but is NOT called from elsewhere in Meza, and therefore is not documented anywhere as a feature of Meza.

This self-contained script clones the testssl.sh GitHub repository, which is software that allows you to "Test TLS/SSL encryption anywhere on any port". So, the script is an unfinished feature in Meza that can test whether the setup is properly encrypted (for traffic).

The functionality ("test my TLS") could be incorporated into a new role, which could then be incorporated into various playbooks. Or, it could simply be added to Meza documentation as instructions for Administrators to use to test their setups.