fix: hyprpaper not starting without hyprpaper.conf

[adamperkowski]

hyprpaper fails if there is no config file available:

[LOG] Welcome to hyprpaper!
built from commit  ()
terminate called after throwing an instance of 'std::runtime_error'
  what():  Could not find config in HOME, XDG_CONFIG_HOME, XDG_CONFIG_DIRS or /etc/hypr.
[1]    16517 IOT instruction (core dumped)  hyprpaper

this adds a check for ~/.config/hypr/hyprpaper.conf and creates the file (with parent dirs) if it doesn't exist