Add setup steps to React native

.docs/content/2.essentials/0.usage-on-x.md

@@ -39,6 +39,23 @@ const providers = makeProviders({
 ```
 
 ## React native
+To use the library in a react native app, you would also need a couple of polyfills to polyfill crypto and base64.
+
+1. First install the polyfills:
+```bash
+npm install @react-native-anywhere/polyfill-base64 react-native-quick-crypto
+```
+
+2. Add the polyfills to your app:
+```ts
+// Import in your entry file
+import '@react-native-anywhere/polyfill-base64';
+```
+
+And follow the [react-native-quick-crypto documentation](https://github.com/margelo/react-native-quick-crypto) to set up the crypto polyfill.
+
+3. Then you can use the library like this:
+
 ```ts
 import { makeProviders, makeStandardFetcher, targets } from '@movie-web/providers';