Tablet UI improvements

[micahlt]

This issue will track UI improvements to make Itchy a better experience on Android tablets/Chromebooks and iPadOS.

• Android rail navigation/iOS sidebar adaptable navigation
• Multi-column layout when screen is horizontal

[micahlt]

FYI, spending a lot of time building out Android rail support for callstack/react-native-bottom-tabs#149 which is part of this.

[micahlt]

Proof of concept for Android rail support on React Native: callstack/react-native-bottom-tabs#407