[Notifications] Add padding to notifications
Summary: This patch aims to add padding to the notification widget and fully remedy the issues that arise once it is applied.
(More padding, and margins as even as can be)
Subscribers: broulik, Codezela, abetts, filipf, davidedmundson, hein, ndavis, plasma-devel
Differential Revision: https://phabricator.kde.org/D17975