Improve toggle mode button

android/gradle.properties

assets/skins/default_button_mark_mine_off.png

assets/skins/default_button_mark_mine_on.png

assets/skins/default_indicator_report_off.png

assets/skins/default_indicator_report_on.png

assets/skins/default_indicator_walk_off.png

assets/skins/default_indicator_walk_on.png

fastlane/metadata/android/en-US/changelogs/33.txt

fastlane/metadata/android/fr-FR/changelogs/33.txt

icons/build_game_icons.sh

icons/skins/default/button_mark_mine_off.svg

icons/skins/default/button_mark_mine_on.svg

icons/skins/default/indicator_report_off.svg

icons/skins/default/indicator_report_on.svg

icons/skins/default/indicator_walk_off.svg

icons/skins/default/indicator_walk_on.svg

lib/layout/board.dart

lib/screens/home.dart