Add missing GNOME 42, 43, 44, 45 wallpapers

Resolves #20 (closed)

Adds missing GNOME 42, 43, 44, and 45 wallpapers sourced from this repository.

• 42
  • light https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/45b15d69bc81ac695ef8418f64eea30fef516395/backgrounds/adwaita-l.jpg
  • dark https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/45b15d69bc81ac695ef8418f64eea30fef516395/backgrounds/adwaita-d.jpg
• 43
  • light https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/4a43eae8b1c06e79dd60a8920167590f2415eb2d/backgrounds/adwaita-l.webp
  • dark https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/4a43eae8b1c06e79dd60a8920167590f2415eb2d/backgrounds/adwaita-d.webp
• 44
  • light https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/b2e4336f0f979e4055add961436d14e566190bcf/backgrounds/adwaita-l.webp
  • dark https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/b2e4336f0f979e4055add961436d14e566190bcf/backgrounds/adwaita-d.webp
• 45
  • light https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/d6f68f843c4334b712c7e2ff4748a0842f4a7847/backgrounds/adwaita-l.jpg
  • dark https://gitlab.gnome.org/GNOME/gnome-backgrounds/-/blob/d6f68f843c4334b712c7e2ff4748a0842f4a7847/backgrounds/adwaita-d.jpg

Found the release dates for each GNOME release via the following blog posts.

• https://foundation.gnome.org/2022/03/23/introducing-gnome-42/
• https://foundation.gnome.org/2022/09/21/introducing-gnome-43/
• https://foundation.gnome.org/2023/03/22/introducing-gnome-44/
• https://foundation.gnome.org/2023/09/20/introducing-gnome-45/

Notes

• Pre-GNOME 42 default wallpapers had three variants: morning, day, and night. GNOME 42 onward default wallpapers only came in light and dark variants. To handle this discrepancy without updating the wallpaper switching logic, GNOME 42 onward light wallpaper was mapped to both morning and day and the dark wallpaper to night.
• GNOME 43 and 44 shipped webp wallpapers. The wallpaper switching code explicitly expects jpg. Thus, I converted the webp to jpg using cloudconvert.
• GNOME 45 planned to ship jxl (not webp) wallpapers but reverted to standard jpg wallpapers, see: GNOME/gnome-backgrounds@3fa3666d. Thus, no conversion needed.