Add icon to "Move to Desktop/Activity" task manager context menu item and fix capitalizations
Summary:
Test Plan: Open the context menu for a task manager item.
Reviewers: Plasma, VDG, ngraham, davidedmundson
Reviewed By: Plasma, VDG, ngraham, davidedmundson
Subscribers: ngraham, VDG, plasma-devel, Plasma
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D23776