Add mock API and reorg code for clarity

src/App.native.tsx

@@ -1,7 +1,8 @@
+import 'react-native-url-polyfill/auto'
 import React, {useState, useEffect} from 'react'
 import {whenWebCrypto} from './platform/polyfills.native'
 import {RootStore, setupState, RootStoreProvider} from './state'
-import * as Routes from './routes'
+import * as Routes from './view/routes'
 
 function App() {
   const [rootStore, setRootStore] = useState<RootStore | undefined>(undefined)