(feat) Make desktop toast notifications cross platform

[dfgHiatus]

Currently, desktop notifications only show on Windows. This could also also be present on MacOS and Linux.

[dfgHiatus]

I found these libs, MIT Licensed:

• https://github.com/ms7m/notify-py
• https://github.com/samschott/desktop-notifier

EDIT: On notify-py's wiki:

As it stands (May 18, 2020), this is simply a notification service. There is no support for embedding custom actions (buttons, dialogs) regardless of platform. Other then telling you if the shell command was sent, there is also no confirmation on user action on the notification.

[dfgHiatus]

On desktop-notifier's issues: samschott/desktop-notifier#11:

You can still develop and debug on a mac but you will either need to manually sign the Python executable or (better option) install Python from https://python.org/ which installs a signed framework build.

TL;DR, unless we sign our code ($99/year, thank you Apple very cool) desktop notifications on MacOS aren't really gonna be a thing, especially with button interactions. notify-py seems to be plagued by the same issue.

[dfgHiatus]

Going to rest on the MacOS stuff, but if we ever need a workaround there's this: https://stackoverflow.com/questions/48856158/change-icon-of-notification-when-using-osascript-e-display-notification

osascript -e 'tell application "Finder"' -e 'activate' -e 'display dialog "this is the note icon." with icon note' -e 'end tell'