Update documentation

Having a good README and a user manual can help users better understand how to use and interact with the product.

Acceptance criteria

• Update the README to match the guidelines described here
• Add a user manual containing the following points:
• Cover the different screens on the Android app
• Cover the information displayed on the Wio screen
• Give examples on the user flow for some functionalities (turning on and connecting the wiomote, changing volume etc)