Include SystemD service unit
Description:
Currently, the extra/hyprpaper package doesn't include the service unit that is provided in their repository. This makes end users couldn't follow the instruction of setting up with uwsm as mentioned in their docs.
Additional info:
- package version:
0.7.1-3 - documentation: https://wiki.hyprland.org/Hypr-Ecosystem/hyprpaper/#run-at-startup
- upstream service unit: https://github.com/hyprwm/hyprpaper/blob/main/systemd/hyprpaper.service.in