Add light/dart theme setting

android/gradle.properties

assets/translations/en.json

assets/translations/fr.json

fastlane/metadata/android/en-US/changelogs/36.txt

fastlane/metadata/android/fr-FR/changelogs/36.txt

lib/cubit/theme_cubit.dart

lib/cubit/theme_state.dart

lib/main.dart

lib/ui/widgets/settings_form.dart

lib/ui/widgets/theme_card.dart

pubspec.yaml