Fix build instructions for gnome 40 and newer
(I.e. use meson instead of autotools)
And add a release entry for latest Ubuntu LTS release 20.04
(Fixes gnome-pomodoro/gnome-pomodoro#570 by showing correct gnome-pomodoro branch to use and correct build instructions for this OS)
Fix build instructions for gnome 40 and newer (I.e. use meson instead of autotools)
And add a release entry for latest Ubuntu LTS release 20.04 (Fixes gnome-pomodoro/gnome-pomodoro#570 by showing correct gnome-pomodoro branch to use and correct build instructions for this OS)