Add GNOME specific wallpapers with a good contrast, so lables for
launchers on top of the wallpaper can be read nicely.
Also set myself as maintainer since the original maintainer didn't
change the package since 2018.
At the moment we have Contributor: lines on some packages (but not all of them),
but often they don't represent the actual contributors to the package very well.
E.g. when we added them retroactively to the device packages we only added
the initial contributor (which isn't necessarily the person
who made most of the work for a device...)
The Git history is the most representative source for figuring out
who contributed to a package, so there is no reason to duplicate that
into the APKBUILD.
[skip ci]: way too many packages
