Adding surface component.

src/components/Surface.js

@@ -0,0 +1,11 @@
+import React from 'react'
+import {View} from 'react-native'
+import {useTheme} from '../lib/theme'
+
+export default function Surface({children, style, ...props}) {
+  const {colors} = useTheme()
+  const baseStyle = {
+    backgroundColor: colors.background,
+  }
+  return <View style={[baseStyle, style]} {...props}>{children}</View>
+}