Fix Certification extraction step

[strk]

Reading the README I understand the certification extraction step is not getting the correct certificate, better at least keep track of the problem. I'd love to be able to sign invoices autonomously (although the infocamere free service at least makes it a bit easier to swallow the requirement: https://fattura-pa.infocamere.it/fpmi/service)

BTW, should this whole repo, README and issue be in italian ? :)