[core] Event emitter

[davidkpiano]

The new emit(…) action creator emits events that can be received by listeners. Actors are now event emitters.

import { emit } from 'xstate';

const machine = createMachine({
  // ...
  on: {
    something: {
      actions: emit({
        type: 'emitted',
        some: 'data'
      })
    }
  }
  // ...
});

const actor = createActor(machine).start();

actor.on('emitted', (event) => {
  console.log(event);
});

actor.send({ type: 'something' });
// logs:
// {
//   type: 'emitted',
//   some: 'data'
// }

[changeset-bot]

🦋 Changeset detected

Latest commit: 10f8dca

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
xstate	Minor

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