Created a new Expo app

hooks/useColorScheme.ts

@@ -0,0 +1,8 @@
+import { ColorSchemeName, useColorScheme as _useColorScheme } from 'react-native';
+
+// The useColorScheme value is always either light or dark, but the built-in
+// type suggests that it can be null. This will not happen in practice, so this
+// makes it a bit easier to work with.
+export default function useColorScheme(): NonNullable<ColorSchemeName> {
+  return _useColorScheme() as NonNullable<ColorSchemeName>;
+}