https://medium.com/google-design/designing-adaptive-icons-515af294c783
https://github.com/bamlab/react-native-make
Create a square image of at least 2208x2208 pixels Make sure to have plenty of margin around your symbol
Next, install the toolbox as well as ImageMagick:
npm install -g yo@2.0.5 generator-rn-toolbox@3.8.0
brew install imagemagick
Now place your image inside of your project, close the workspace inside of XCode and run the following command:
yo rn-toolbox:assets --splash image.png --ios
source: https://developer.okta.com/blog/2019/04/05/react-native-ios-app-store