How to use 'web_socket_channel' in todos_repository_simple

### Web socket as data Provider

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`todos_repository_simple` explains nicely about the benefits of using repository as singleton. But no where it's mentioned how to handle the web sockets.

How can I use web socket (webSocket and fileStorage) instead of rest (webClient and fileStorage) ?

Some key points between web socket and rest.
- The name itself signify socket is stateLess and rest is stateFull
- socket is bidirectional : Server can send data to client and client will have a callback to perform accordingly and vice versa.

> My dataProvider is `socket and fileStorage` and follows `flutter_bloc `architecture.

**Every time we receive data from socket :**
[Article](https://www.didierboelens.com/2018/06/web-sockets---build-a-real-time-game/) : reload the UI directly in widget by mapping switch case.
[Flutter_bloc](https://github.com/felangel/bloc/tree/master/examples/flutter_todos): need to reload the UI through bloc_state.

Thanks.

No file or test is named. Start by reviewing the todos_repository_simple example and its current REST provider structure, then compare it with the requested web_socket_channel and fileStorage approach. Done means documenting how socket updates flow through the repository and flutter_bloc state so the UI can react to server messages.

Written by the indexing model from the issue text.