[docs] [issue17006] Add advice on best practices for hashing secrets

Antoine Pitrou added the comment: Note boxes have nothing to do with warnings, we should discuss them separately if needed. (I see nothing wrong with multiple notes, given that a note is generally something ancillary and optional) ---------- nosy: +pitrou _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue17006> _______________________________________