Update manifest.json

manifest.json

@@ -3,8 +3,9 @@
   "short_name": "eUM",
   "start_url": "/",
   "display": "fullscreen",
-  "background_color": "#f8f9fa",
-  "theme_color": "#f8f9fa",
+  "orientation": "portrait",
+  "background_color": "#000000",
+  "theme_color": "#000000",
   "icons": [
     {
       "src": "/icon.png",
@@ -12,4 +13,4 @@
       "type": "image/png"
     }
   ]
-}
+}