Translation mode: Add Notification mode

Created by: rainbowhxch

Hello, thank you very much for writing such a good tool.

I have been using i3-wm under Linux, but when I use crow, the main translation window that pops up often changes the layout of opened applications. So, I've always wanted crow to have a function to display translation results based on system notification. I added some code on the basis of the program and wrote a demo. I don't know if this can be useful or if you have plans to add it. Please feel free to choose whether to use it or not. I'm a new QT player, so I don't know if there's a better way.