Add mouse button icons

Summary:
Add left, middle and right click icons for KDE Connect

FEATURE: 399295
FIXED-IN: 5.53

Test Plan:

Reviewers: VDG, ngraham, nicolasfella, KDE Connect

Reviewed By: VDG, ngraham, nicolasfella, KDE Connect

Subscribers: trickyricky26, abetts, ngraham, rizzitello, nicolasfella, kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D16951