Create package for more operating systems/linux distros

[kantord]

Someone already created a package for Arch linux: https://aur.archlinux.org/packages/i3-gnome-pomodoro-git

To my knowledge, there are no packages for any other OS yet :thinking:

By the way, installing the Arch package lets you use it simply by calling i3-gnome-pomodoro instead of pomodoro-client.py. I think it would be nice to keep that for the other packages, so that we can use that in the documentation