readme: add graphql subscription info

Author: arnaudbzn

README.md

@@ -1,6 +1,7 @@
 # React Native - React Query - Hasura - demo app 
 
 A basic React Native app to demonstrate [React Query](https://react-query.tanstack.com/) with [GraphQL Code generator](https://www.graphql-code-generator.com/) features. 
+
 The GraphQL API is powered by [Hasura](https://hasura.io).
 
 ## React Native EU Conference 2021 Talk
@@ -9,6 +10,8 @@ The GraphQL API is powered by [Hasura](https://hasura.io).
 
 The app folders structure has been updated in this repo compared to the version demonstrated in the talk.
 
+GraphQL subscription support example has been added.
+
 ## Full Stack
 ### Front-end
 - Expo
@@ -133,11 +136,13 @@ To generate types and operations with GraphQL code generator (Hasura must be up)
 - [X] React Suspense and Error boundaries support
 - [X] FlatList with infinite queries
 - [X] Cache persistence in the Async storage
+- [X] GraphQL subscriptions
 
 ## Branches
 - `main` Demo app with infinite list, async storage persistor and optimistic updates
 - `simple-list` Demo app using a simple movies FlatList
 - `movies-list-optimistic-update` The movies list is optimistically updated after a movie mutation 
+- `graphql-subscriptions` the movie details screen is updated with GraphQL subscriptions
 
 ## Notes
 - This app uses many auto-refetch and cache invalidation possibilities but you may have to select the ones you really need for your app in production.
@@ -147,4 +152,4 @@ To generate types and operations with GraphQL code generator (Hasura must be up)
 - No GraphQL API authentication and authorization have been implemented in this demo.
 - React Native Web support is experimental.
 - Console logs are verbose for demo purposes.
-- GraphQL subscriptions are not demonstrated in this app but [React Query can be used with web sockets](https://tkdodo.eu/blog/using-web-sockets-with-react-query).
+- More info about WebSocket support in this article [React Query can be used with web sockets](https://tkdodo.eu/blog/using-web-sockets-with-react-query).