add support for bitwarden

[ayushnix]

The official bitwarden CLI isn't really human friendly but it does output JSON and that can be parsed with jq. An unofficial cli, rbw, seems like a much more human friendly interface.

It seems like there are already several dmenu wrapper projects for both the official CLI and for rbw. Still, it should be interesting to add support for bitwarden in tessen. We already support pass and gopass. I intend to add support for both the official CLI and rbw in the next major release of tessen.

[ayushnix]

bitwarden-rofi exists as well