Provide support for `waldo add` and `waldo build` for Expo (React Native)

[edelans]

same as #20, but with EXPO React Native

[edelans]

expo doc looks very clean, and the process looks very straigthfwd

• https://docs.expo.dev/build-reference/simulators/ : command to generate iOS simulator builds
• https://docs.expo.dev/build-reference/apk/ for Android