Add flameshot tray icons

Summary: Add the system tray icon for flameshot. This patch adds some icons following the breeze style.

Test Plan:
Before:

After:

Reviewers: VDG, ngraham, ndavis

Reviewed By: VDG, ngraham, ndavis

Subscribers: ndavis, ngraham, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D27926