Bug: Invoke configuration does not support string type when given array

[viglucci]

Description

There are type errors when attempting to use a string as the name of a state in the onDone or onError portion for an invoked service, even though this should be considered a perfectly valid configuration, and without typescript functions just fine.

Expected result

The following simple machine should not cause type errors:

import { createMachine } from "xstate";

createMachine({
    invoke: {
        src: () => () => { },
        onDone: [{ target: "a" }, "b"],
    },
    states: {
        a: {},
        b: {},
    },
});

Actual result

Typescript is unhappy:

Type '{ src: () => () => void; onDone: (string | { target: string; })[]; }' is not assignable to type 'SingleOrArray<AnyStateMachine | InvokeConfig<unknown, AnyEventObject>>'.
  Types of property 'onDone' are incompatible.
    Type '(string | { target: string; })[]' is not assignable to type 'string | SingleOrArray<TransitionConfig<unknown, DoneInvokeEvent<any>>>'.
      Type '(string | { target: string; })[]' is not assignable to type 'TransitionConfig<unknown, DoneInvokeEvent<any>>[]'.
        Type 'string | { target: string; }' is not assignable to type 'TransitionConfig<unknown, DoneInvokeEvent<any>>'.
          Type 'string' has no properties in common with type 'TransitionConfig<unknown, DoneInvokeEvent<any>>'.ts(2322)

Reproduction

https://codesandbox.io/s/currying-shadow-8tnshi?file=/src/index.ts

Additional context

Originally reported here: statelyai/xstate-tools#275

[Andarist]

This was fixed by #3745