Improve transitions in dark scheme

[mgonzalezg9]

When changing between screens the light mode is applied in the first render, so the user gets to see a white trail in the app.

• It might be useful to use system colors instead of white and black colors defined in the application.
• Check how expo suggest to implement this in the following tutorial.
• useColorScheme is a hook for retrieving the user's selected mode. It could be useful to create a custom hook wrappping it along with the color selection.