Adapt our docs style to material.io style

[ferrannp]

Our docs: https://callstack.github.io/react-native-paper/toolbar.html should be similar to Google docs https://material.io/guidelines/layout/principles.html#

• Nicer sidebar
• Use more colors (for titles)
• Typography

So we have:

• Header with component name (like Layout screen from material.io)
• Small description (1 line)
• Usage - Screenshots
• Props

[jukben]

More Material UI style callstack/component-docs#6

screenshots still pending...