add notification keybinds

[bob8677]

Current keybindings:

• super + ctrl + up to close most recent notification
• super + ctrl + down to pull notifications from history
• super + ctrl + enter to open the context menu for action

Things that can change:

• Keys
• Adding close all (dunstctl close-all)
• Possibly removing the history part if it is not wanted

If this does get approved, changing the history_length option in dunstrc to make the history part more useful would make sense.