Security: add port knocking support

To significantly improve security it would be wonderful if the Bitwarden clients would support port knocking (personally I use the macOS app and Firefox extension).

New Settings:

  • port knocking sequence: (e.g. 7000,8000,9000)
  • port knocking sequence timeout: (5s)
  • port knocking timeout: (1m)
  • port knocking payloads

https://manpages.debian.org/testing/knockd/knockd.1.en.html
https://help.ubuntu.com/community/PortKnocking