Add icon

flutter/web/manifest.json

@@ -3,8 +3,8 @@
     "short_name": "simplecloudnotifier",
     "start_url": ".",
     "display": "standalone",
-    "background_color": "#0175C2",
-    "theme_color": "#0175C2",
+    "background_color": "#hexcode",
+    "theme_color": "#hexcode",
     "description": "A new Flutter project.",
     "orientation": "portrait-primary",
     "prefer_related_applications": false,
@@ -32,4 +32,4 @@
             "purpose": "maskable"
         }
     ]
-}
+}