Add DesktopEntry to notifyrc
Summary:
This allows the notification KCM to identify akregator as an
application.
Test Plan:
Checked that akregator shows up under applications in the
new KCM.
Reviewers: KDE PIM, broulik
Subscribers: kde-pim
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D21117