Suggestion: Full screen (f11) feature

[camilogonzzzz]

Hi! First of all, thanks for the great Pomodoro timer, been using it a lot and really like the design, the aesthetics and the features.
I wanted to suggest, if its possible (im not really a github experienced user), a true fullscreen mode (f11). I know this might be a bit personal or even a bit picky, but seeing the Windows taskbar creates some visual noise for me. It would feel more aesthetically pleasing and help me focus better if I could hide everything and just see the timer.

Thanks again for your work!

[Splode]

This is implemented now with #382, which also provides support for local shortcuts (keybindings while the timer window is focused, as opposed to global shortcuts).