Recommend pod-install for setup instructions

We've been recommending devs use `npx pod-install` since it will attempt to install cocoapods CLI if it's not available on the computer (cite [React Navigation setup guide](https://reactnavigation.org/docs/getting-started/#installing-dependencies-into-a-bare-react-native-project)). This has proved very useful for Expo users who are now migrating to the bare workflow and want to use community packages in their projects.

Author: EvanBacon

README.md

@@ -37,8 +37,7 @@ react-native link @react-native-community/blur
 3. (iOS only) Install to Xcode:
 
 ```
-cd ios
-pod install
+npx pod-install
 ```
 
 4. (Android only, optional)