Add support to notify the user when a command has finished

[zenangst]

When configuring a command, the user can check a box called Notify.
Right now it doesn't do anything, so we should really implement this feature 🤡

It is undecided what this should look like, and where it should appear.
Perhaps we should consider configuring what kind of notification should appear: front and center | notification center | show keystrokes

[zenangst]

I started tinkering with a "bezel" notification earlier.

Screen.Recording.2023-06-05.at.15.57.54.mov

[zenangst]

It would be nice if you could make the notification state something, or even get the output from a terminal or script command.

So if you toggle, Let's say "Lower power mode" via a shell script, it would get the output from the command and use that to indicate to the user if the command was toggle on or off.

This could be a really neat improvement.