[questions/qa-personal-names] Add some description for German honorifics

[xfq]

https://www.w3.org/International/questions/qa-personal-names#formality

In Germany, titles are important, and you may need to refer to someone as not just Herr Schmidt, but Herr Professor Doktor Schmidt.

It may be more helpful for readers who are not familiar with German to explain what "Herr" means. Maybe something like "the equivalent of Mr. or Sir"?