Default backdrop

[SpaghettiC0des]

Feature Request

Provide a default backdrop/background component with a translucent background color.

Why it is needed

To distinguish that the bottom sheet is visible, or it pops out when the UI behind is mostly color white.

Possible implementation

backgroundComponent should have a default implementation, I'm thinking it is also useful to export that component as BottomSheetBackdrop so that users can provide custom styling.

noBackdrop prop will also help to disable the default backdrop component.

Code sample

import BottomSheet, {BottomSheetBackdrop} from '@gorhom/react-native-bottom-sheet`;

const MyBackdrop = () => <BottomSheetBackdrop style={{
	backgroundColor: 'red',
}}/>

<BottomSheet />
<BottomSheet noBackdrop/>
<BottomSheet backgroundComponent={MyBackdrop}/>