Fetch the packages for the project (important)

Run this command on your project folder

flutter pub get

More info: https://flutter.dev/docs/development/packages-and-plugins/using-packages

Focus on this statement:

• From the terminal: Run flutter pub get. OR

• From Android Studio/IntelliJ: Click Packages get in the action ribbon at the top of pubspec.yaml.

• From VS Code: Click Get Packages located in right side of the action ribbon at the top of pubspec.yaml.

Then, do the same thing for the local package: packages/den_lineicons.