[Feature request] Center the task list

[Barbaross93]

Describe the solution you'd like

What would be nice is that for the task window as well as completed task window the contents are centered in the middle of the window similar to how gnome-todo presents the task list. This would also follow the layout of the timer window as the contents there are centered in the window.

Describe alternatives you've considered

I've tried putting in my own custom gtk.css to achieve this in ~/.config/gtk-3.0/gtk.css but I'm not proficient enough to know how to target the gtk application in addition to the particular property.