Connection with client certificate

[JunjiUmeno]

TLS not supported yet? Hope it will support connection by client certificate, so clients can connect to AWS IoT or simliar products.

[MilanJovic92]

Hi JunjiUmeno,
Thank you for the interest in this library, your suggestion is valid and I would like to add it as a feature.
However I do not have enough time to work on this, so if you would like feel free to create PR and I would be happy to merge it.