[@xstate/react] Expose error snapshots in useActor/useMachine

[davidkpiano]

useActor (and useMachine by alias) now properly re-renders when an action throws, exposing status: 'error' and error on the snapshot.

const App = () => {
  // Machine that might throw an error, e.g.:
  // entry: () => throw new Error('error');
  const [state, send, actor] = useActor(machine);

  const errorMessage = state.status === 'error' ? (state.error as Error)?.message : null;
  
  // ...
};

Fixes #5455

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Latest commit: c17371a

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

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[Andarist]

shouldnt this also have complete: handleStoreChange?

[Andarist]

this might sound controversial but I'd consider doing this in the useActor's implementation:

if (actorSnapshot.status === 'error') throw actorSnapshot.error;

[davidkpiano]

I'm not opposed to this 🤔