feat(client): Async iterator for subscriptions

[enisdenjo]

The iterate method on the client allows async iteration over the subscription events.

import { createClient } from 'graphql-ws';

const client = createClient({
  url: 'ws://localhost:4000/graphql',
});

// query
(async () => {
  const query = client.iterate({
    query: '{ hello }',
  });

  const { value } = await query.next();
  expect(value).toEqual({ hello: 'world' });
})();

// subscription
(async () => {
  const subscription = client.iterate({
    query: 'subscription { greetings }',
  });

  for await (const event of subscription) {
    expect(event).toEqual({ greetings: 'Hi' });

    // complete a running subscription by breaking the iterator loop
    break;
  }
})();

TODO

• Overload subscribe method Cannot overload interface method with different return types microsoft/TypeScript#54354

[github-actions]

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[enisdenjo]

🎉 This PR is included in version 5.14.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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