docs: update theme and background colors in web manifest

Author: devopvoid

docs/public/apple-touch-icon.png

@@ -15,7 +15,7 @@
       "purpose": "maskable"
     }
   ],
-  "theme_color": "#ffffff",
-  "background_color": "#ffffff",
+  "theme_color": "#1e0959",
+  "background_color": "#1e0959",
   "display": "standalone"
 }