New wallpaper and README banner (MR 26)

README.md

-# artwork
+<div align="center">
+
+<img src=/src/banner.svg>
+
+</div>
 
 ### Attribution
-src/pmos-grass.blend: CC-BY 3.0 Grass background by https://www.blendswap.com/user/Spelle
+
+1. src/pmos-grass.blend: CC-BY 3.0 Grass background by https://www.blendswap.com/user/Spelle
+1. /wallpapers/2024 & /src/banner.svg: CC-BY-SA 3.0 release wallpapers and readme artwork by https://gitlab.com/dikasetyaprayogi

wallpapers/README.md

+released wallpapers are synced here: https://wiki.postmarketos.org/wiki/Wallpapers