deskutils/fyi: new port

FYI (for your information) is a command line utility to send desktop
notifications to the user via a notification daemon implementing XDG desktop
notifications.

It is a almost a notify-send clone, with the following differences:

• notify-send does not implement --close.
• notify-send does not expose activation tokens (needed for window focus/activation) in any meaningful way. It prints it as a debug message when G_MESSAGES_DEBUG=all; fyi prints it when you use --print-token.
• fyi has consistent syntax in its --action and --hintoptions.
• fyi can print the reason a notification was closed, with --print-reason.
• fyi can query the notification daemon for its name and version information.
• fyi can query the notification daemon for its capabilities.
• fyi has shell completions (bash and fish).
• fyi has a single run-time dependency: dbus.