Add click to play/pause feature on previews for audio/video
Test Plan:
In dolphin, click on a video or audio preview in the information panel.
The video or audio preview starts
Reviewers: elvisangelaccio, Dolphin, ngraham
Reviewed By: elvisangelaccio, Dolphin, ngraham
Subscribers: alexde, anthonyfieroni, ngraham, kfm-devel
Tags: Dolphin
Differential Revision: https://phabricator.kde.org/D22183