wallpapers/potd: Add "About image" context menu entry
Allows to quickly access the website with information about the displayed image.
I found it nifty how Windows places a “learn more about this image” pseudo file on the desktop that opens the website.
XDG Activation doesn’t seem to work properly, I assume that’s Qt.openUrlExternally being too late after the QMenu is already closed.
Edited by Kai Uwe Broulik
