make loading message account for dark mode & add i18n (#2033)

* make loading message account for dark mode & add i18n

* use app color scheme

src/components/LoadingMessage.tsx

@@ -1,10 +1,11 @@
 import React from "react";
+import { t } from "../i18n";
 
 export const LoadingMessage = () => {
   // !! KEEP THIS IN SYNC WITH index.html !!
   return (
     <div className="LoadingMessage">
-      <span>{"Loading scene..."}</span>
+      <span>{t("labels.loadingScene")}</span>
     </div>
   );
 };

src/locales/en.json

@@ -68,7 +68,8 @@
     "toggleGridMode": "Toggle grid mode",
     "addToLibrary": "Add to library",
     "removeFromLibrary": "Remove from library",
-    "libraryLoadingMessage": "Loading library..."
+    "libraryLoadingMessage": "Loading library...",
+    "loadingScene": "Loading scene..."
   },
   "buttons": {
     "clearReset": "Reset the canvas",