chore: add documentation about polyfills needed to use text streaming in RN

docs/source/data/defer.mdx

@@ -79,3 +79,7 @@ For this reason, `@defer` can be thought of as a tool to improve initial renderi
 ## Using with code generation
 
 If you currently use [GraphQL Code Generator](https://www.the-guild.dev/graphql/codegen) for your codegen needs, you'll need to use the Codegen version `4.0.0` or higher. Please refer to the [Codegen documentation](https://the-guild.dev/graphql/codegen/plugins/presets/preset-client#fragment-masking-with-defer-directive) for more information.
+
+## Usage in React Native
+
+In order to use `@defer` in a React Native application, additional configuration is required. See the [React Native docs](../integrations/react-native#consuming-multipart-http-via-text-streaming) for more information.

docs/source/data/directives.mdx

@@ -74,6 +74,8 @@ query PersonQuery($personId: ID!) {
 }
 ```
 
+> **Note:** in order to use `@defer` in a React Native application, additional configuration is required. See the [React Native docs](../integrations/react-native#consuming-multipart-http-via-text-streaming) for more information.
+
 For more information about the `@defer` directive, check out the [`@defer` docs](/react/data/defer).
 
 ## `@export`

docs/source/data/subscriptions.mdx

@@ -199,10 +199,12 @@ const wsLink = new GraphQLWsLink(createClient({
 
 Your `GraphQLWsLink` passes the `connectionParams` object to your server whenever it connects. Your server receives the `connectionParams` object and can use it to perform authentication, along with any other connection-related tasks.
 
-## Subscriptions via Multipart HTTP
+## Subscriptions via multipart HTTP
 
 No additional libraries or configuration are required. Apollo Client adds the required headers to your request when the default terminating `HTTPLink` receives a subscription operation at the `uri` specified when initializing the link or Apollo Client instance.
 
+> **Note:** in order to use subscriptions over multipart HTTP in a React Native application, additional configuration is required. See the [React Native docs](../integrations/react-native#consuming-multipart-http-via-text-streaming) for more information.
+
 ## Executing a subscription
 
 You use Apollo Client's `useSubscription` Hook to execute a subscription from React. Like [`useQuery`](./queries/#executing-a-query), `useSubscription` returns an object from Apollo Client that contains `loading`, `error`, and `data` properties you can use to render your UI.

docs/source/integrations/react-native.md

@@ -44,6 +44,35 @@ For more information on setting up Apollo Client, see [Getting started](../get-s
 2. Enable "Debug JS Remotely" in your app.
 3. If you don't see the Developer Tools panel or the Apollo tab is missing from it, toggle the Developer Tools by right-clicking anywhere and selecting **Toggle Developer Tools**.
 
+## Consuming multipart HTTP via text streaming
+
+By default, React Native ships with a `fetch` implementation built on top of XHR that does not support text streaming.
+
+For this reason, if you are using *either* [`@defer`](../data/defer) or [subscriptions over multipart HTTP](../data/subscriptions#subscriptions-via-multipart-http)—features that use text streaming to read multipart HTTP responses—there are additional steps you'll need to take to polyfill this functionality.
+
+1. Install `react-native-fetch-api` and `react-native-polyfill-globals` and save them both as dependencies.
+2. In your applications entrypoint (i.e. `index.js`, `App.js` or similar), import the following three polyfille, and call each of the `polyfill*` functions before any application code:
+```tsx
+import { polyfill as polyfillEncoding } from "react-native-polyfill-globals/src/encoding";
+import { polyfill as polyfillReadableStream } from "react-native-polyfill-globals/src/readable-stream";
+import { polyfill as polyfillFetch } from "react-native-polyfill-globals/src/fetch";
+
+polyfillReadableStream();
+polyfillEncoding();
+polyfillFetch();
+```
+1. Finally, there’s a special option we’ll need to pass to our polyfilled `fetch`. Create an `HttpLink` so we can pass the following options in the default `fetchOptions`:
+```tsx
+const link = new HttpLink({
+  uri: "http://localhost:4000/graphql",
+  fetchOptions: {
+    reactNative: { textStreaming: true },
+  },
+});
+```
+
+Now you're ready to use `@defer` and/or multipart subscriptions over HTTP in your React Native app!
+
 ## Troubleshooting
 
 * `Uncaught Error: Cannot read property 'prototype' of undefined`, or similar Metro build error when importing from `@apollo/client`