Design/Wallpapers/Change the default wallpaper

1. Get VDG agreement on the wallpaper.
2. Have git checkouts of the plasma wallpaper updater, breeze, plasma-workspace, plasma-desktop, and plasma-workspace-wallpapers git repos.
3. Follow the instructions at https://invent.kde.org/plasma/plasma-wallpaper-updater#how-to-use-it.
4. In each of the breeze, plasma-workspace, plasma-desktop, and plasma-workspace-wallpapers repos, push the newly-created branch to origin and open a merge request.
5. Merge once the pipeline is green!