Adds right-click menu option for image files: 'Set As Wallpaper'.
Changes background image path in both /root/.config/wallpaper/bg_img and /root/.jwm/jwmrc-wallpaper
Can also be run from the command line with the full image path:
# change_wallpaper /root/Backgrounds/codioful.jpg
Background set successfully.
Updated /root/.config/wallpaper/bg_img with the new background path.
Updated /root/.jwm/jwmrc-wallpaper with the new background path.