[Wallpaper] Allow adding multiple images at once from the file picker dialog
Summary:
BUG: 402223
FIXED-IN: 5.15.0
Test Plan: Added multiple images from the file dialog. They all showed up in the wallpaper grid.
Reviewers: Konsole, broulik, davidedmundson
Reviewed By: davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D17815