systray: show a small animation on the icons when activated
Summary: Both for plasmoids and SNI
Test Plan: Now there's some kind of feedback when pressing the icons
Reviewers: Plasma, ngraham
Reviewed By: ngraham
Subscribers: filipf, broulik, anthonyfieroni, davidedmundson, ngraham, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D19947