Header should blend with status bar on Android devices

[joebochill]

Describe the desired behavior

The header should blend behind the StatusBar on android devices (particularly those with a notch).

Describe the current behavior

Currently the Header is drawn below the StatusBar on Android devices.

Is this request related to a current issue?

This is related to work from the EMCB project.

Additional Context

The StatusBar has a translucent prop that will allow us to draw content behind it (if we set backgroundColor to 'transparent'). However, setting this property currently causes some misalignment with the content because SafeAreaView does not do anything on Android (see facebook/react-native#17371). We will need to manually add a top padding in the Header on Android devices.

[daileytj]

The quick and dirty solution above still needs some investigation since it leaves the middle content slightly visible when collapsed.

[daileytj]

Fixed by #339