feat: add gnome 42 support

closes #1

usr/local/bin/wallpaperctl

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+gversion="0"
 pictureuri="picture-uri"
 
 validate_config() {
@@ -19,9 +20,27 @@ validate_config() {
     fi
 }
 prepare() {
+    get_gnome_version
+    get_gnome_color_scheme
+    set_gnome_color_scheme
     get_wallpaper
     validate_wallpaper
 }
+get_gnome_version() {
+    if [ -r "/usr/share/gnome/gnome-version.xml" ]; then
+        gversion="$(grep -i "platform" /usr/share/gnome/gnome-version.xml | tr -d " <platform>" | tr -d "/")"
+    fi
+}
+get_gnome_color_scheme() {
+    if [ "$gversion" -ge 42 ]; then
+        style="$(gsettings get org.gnome.desktop.interface color-scheme)"
+    fi
+}
+set_gnome_color_scheme() {
+    if [ "$style" = "'prefer-dark'" ]; then
+        pictureuri="picture-uri-dark"
+    fi
+}
 get_wallpaper() {
     selection="$(find "$WALLPAPER_DIR" -type f -name "*.jpg" -o -name "*.png" | shuf -n1)"
 }