add react native polyfill to getting started (#5097)

* add react native polyfill to getting started

* move polyfill to only datastore getting started

* fix typo

Co-authored-by: Tim Nguyen <[email protected]>

* add phrasing suggestions

---------

Co-authored-by: Tim Nguyen <[email protected]>

Author: Dane Pilcher

src/fragments/lib/datastore/native_common/setup-env.mdx

@@ -27,3 +27,7 @@ Instead of using the platform integration, you can alternatively use the Amplify
 import all0 from '/src/fragments/lib/datastore/native_common/setup-env-cli.mdx';
 
 <Fragments fragments={{ all: all0 }} />
+
+import reactnative1 from '/src/fragments/lib/datastore/react-native/getting-started/polyfills.mdx';
+
+<Fragments fragments={{ 'react-native': reactnative1 }} />

src/fragments/lib/datastore/react-native/getting-started/30_platformIntegration.mdx

@@ -12,7 +12,7 @@ Start with the [React Native CLI](https://reactnative.dev/docs/getting-started):
 npx [email protected] init AmplifyDataStoreRN --version 0.68.2
 cd AmplifyDataStoreRN
 npx amplify-app@latest
-npm install aws-amplify @react-native-community/netinfo @react-native-async-storage/async-storage
+npm install aws-amplify @react-native-community/netinfo @react-native-async-storage/async-storage core-js
 ```
 
 You will also need to install the pod dependencies for iOS:
@@ -31,7 +31,7 @@ To enable SQLite with DataStore for enhanced local database performance, follow
 npx [email protected] init AmplifyDataStoreRN --version 0.68.2
 cd AmplifyDataStoreRN
 npx amplify-app@latest
-npm install aws-amplify @aws-amplify/datastore-storage-adapter react-native-sqlite-storage @react-native-community/netinfo @react-native-async-storage/async-storage
+npm install aws-amplify @aws-amplify/datastore-storage-adapter react-native-sqlite-storage @react-native-community/netinfo @react-native-async-storage/async-storage core-js
 npx pod-install
 ```
 

src/fragments/lib/datastore/react-native/getting-started/polyfills.mdx

@@ -0,0 +1,7 @@
+### Add Required Polyfills
+
+React Native is missing some JavaScript standard library functionality that DataStore depends on. Add the following to the entry point of your app to polyfill these missing functionalities:
+
+```js
+import 'core-js/full/symbol/async-iterator';
+```