Add light/dart theme setting

android/gradle.properties

assets/translations/en.json

assets/translations/fr.json

fastlane/metadata/android/en-US/changelogs/57.txt

fastlane/metadata/android/fr-FR/changelogs/57.txt

lib/cubit/theme_cubit.dart

lib/cubit/theme_state.dart

lib/main.dart

lib/ui/widgets/abstracts/custom_chart.dart

lib/ui/widgets/charts/counts_by_day.dart

lib/ui/widgets/charts/counts_by_hour.dart

lib/ui/widgets/charts/discoveries_artists.dart

lib/ui/widgets/charts/discoveries_tracks.dart

lib/ui/widgets/charts/heatmap.dart

lib/ui/widgets/charts/timeline_counts.dart

lib/ui/widgets/charts/timeline_eclecticism.dart

lib/ui/widgets/charts/top_artists.dart

lib/ui/widgets/charts/top_artists_stream.dart

lib/ui/widgets/content/statistics_global.dart

lib/ui/widgets/content/statistics_recent.dart