Create app onboarding

[lpezzolla]

We might use one or both of the following approaches:

• Show some introductory screens (like in https://github.com/jfilter/react-native-onboarding-swiper, possibly without introducing this dependency)
• Highlights UI items (https://github.com/mohebifar/react-native-copilot)

Which information do you feel is important to improve the experience of an user opening it for the first time?