implemented: "apply" button and the correct exiting

ximper-unified-theme-switcher-gui.sh

@@ -93,7 +93,16 @@ NEW_SETTINGS=$(yad --form --columns=2 \
 --field="Kvantum light theme:CB" "$(kv-themes-list light)" \
 --field="Kvantum dark theme:CB" "$(kv-themes-list dark)" \
 --field="GTK3 light theme:CB" "$(gtk3-themes-list light)" \
---field="GTK3 dark theme:CB" "$(gtk3-themes-list dark)")
+--field="GTK3 dark theme:CB" "$(gtk3-themes-list dark)" \
+\
+--button="yad-apply:0" \
+--button="yad-cancel:1" \
+)
+
+if [[ $? == 252 || $? == 1 ]]; then
+    echo "EXIT"
+    exit 0
+fi
 
 IFS='|' read -r KV_LIGHT KV_DARK GTK3_LIGHT GTK3_DARK <<< "$NEW_SETTINGS"
 shell_config_set "$EDITABLE_CONFIG_FILE" KV_LIGHT_THEME "$KV_LIGHT"