[v5] createEmptyActor()

[davidkpiano]

This PR makes it easy to create null actors which only emit undefined.

Especially in @xstate/react, this makes working with maybe-undefined actors easier:

import { createEmptyActor } from 'xstate/actors';

// ...
function Comp({ maybeActor }) {
  const [state, send] = useActor(maybeActor ?? createEmptyActor());

  state?.count; // strongly-typed; state can be undefined
}

[changeset-bot]

🦋 Changeset detected

Latest commit: c03ee88

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

This PR includes changesets to release 1 package

Name	Type
xstate	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit c03ee88:

Sandbox	Source
XState Example Template	Configuration
XState React Template	Configuration

[ghost]

👇 Click on the image for a new way to code review

Legend

[davidkpiano]

Addresses #1416