✨ add language switch, add german

public/locales/en/settings/customization/app-width.json

@@ -0,0 +1,3 @@
+{
+  "label": "App Width"
+}

public/locales/en/settings/customization/page-appearance.json

@@ -14,5 +14,8 @@
   "background": {
     "label": "Background",
     "placeholder": "/img/background.png"
+  },
+  "buttons": {
+    "submit": "Submit"
   }
 }