app icon; minor changes

trackeroo/android/app/src/main/ic_launcher-playstore.png

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

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

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

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

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

trackeroo/assets/icon/kangaroo-circle.png

trackeroo/assets/icon/kangaroo-square.png

...s/Runner/Assets.xcassets/AppIcon.appiconset/Contents.json

...ets.xcassets/AppIcon.appiconset/Icon-App-1024x1024@1x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-20x20@1x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-20x20@2x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-20x20@3x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-29x29@1x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-29x29@2x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-29x29@3x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-40x40@1x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-40x40@2x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-40x40@3x.png

.../Assets.xcassets/AppIcon.appiconset/Icon-App-60x60@2x.png