update assets in pubspec

pubspec.yaml

@@ -45,10 +45,11 @@ flutter:
   uses-material-design: true
 
   # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
-
+  assets:
+    - assets/icons/
+    - assets/images/
+    - assets/animations/
+    - assets/files/
   # An image asset can refer to one or more resolution-specific "variants", see
   # https://flutter.dev/assets-and-images/#resolution-aware.