Merge branch '21-clean-code' into 'master'

android/app/src/main/res/mipmap-hdpi/ic_launcher.png

android/app/src/main/res/mipmap-mdpi/ic_launcher.png

android/app/src/main/res/mipmap-xhdpi/ic_launcher.png

android/app/src/main/res/mipmap-xxhdpi/ic_launcher.png

android/app/src/main/res/mipmap-xxxhdpi/ic_launcher.png

android/gradle.properties

fastlane/metadata/android/en-US/images/featureGraphic.png

fastlane/metadata/android/en-US/images/icon.png

icons/build_application_icons.sh

icons/build_game_icons.sh

icons/featureGraphic.svg

icons/icon.svg

lib/main.dart

pubspec.lock

test/widget_test.dart