Translates the documentation portal into Italian, as suggested by carlavilla.
Carlavilla already gave doc approval, however I ask him for approval again as in the last translated string I changed the syntax for the link, which was left in the original at the syntax of the old tools: please see the original at https://docs.freebsd.org/en/articles/vm-design/ , in the trademarks paragraph.
I will later fix the original as well, unless someone wants to fix it before I find the time.
I ask for review from madpilot as he is the main reference for Italian translations. For reference, most of the translated strings can be found from the main documentation page https://docs.freebsd.org/en/ or from links that can be found on the same page.
I also ask for mentor approval to my mentors gerald and tcberner.
As commit message I would write only "Documentation portal: Translate into Italian", then as metadata I would add mentor approval, doc approval, differential revision. If someone else tests the build I would also write into the "Tested by:".