Improve UI, add custom graphics

android/gradle.properties

assets/skins/default_house.png

fastlane/metadata/android/en-US/changelogs/7.txt

fastlane/metadata/android/fr-FR/changelogs/7.txt

lib/main.dart

lib/models/data/category.dart

lib/models/data/letter.dart

lib/ui/layouts/game_layout.dart

lib/ui/widgets/game/game_board.dart

lib/ui/widgets/game/game_house.dart

lib/ui/widgets/game/game_player.dart

lib/ui/widgets/game/game_score.dart

lib/ui/widgets/game/game_seeds.dart

pubspec.yaml

resources/seeds_layout.svg

resources/ui/skins/default/house.svg