Add a DefaultActorSystem type to replace AnyActorSystem

[hackape]

Currently AnyActorSystem is used everywhere, rendering interface ActorSystem<T extends ActorSystemInfo> useless.

I would love to be able to pass in my own ActorSystemInfo so I can implement dependency injection pattern, allowing one actor to assume the existence of a set of other named actors within the system.

I propose this pattern:

// export type AnyActorSystem = DefaultActorSystem;
export type DefaultActorSystem = ActorSystem<DefaultActorSystemInfo>;

interface DefaultActorSystemInfo { 
    actors: ActorsInDefaultSystem;
}

export interface ActorsInDefaultSystem {
  /** leave empty */
}

Now I can specify in my "app.d.ts":

declare module 'xstate' {
  import type { ActorsInDefaultSystem, ActorRef, AnyActorRef } from 'xstate';
  interface ActorsInDefaultSystem extends Record<string, AnyActorRef> {
    myInjectedActor: ActorRef<any, { type: 'MY_CUSTOM_EVENT' } | { type: 'MY_OTHER_EVENT' }, any>;
    myOtherActor: ActorRef<any, { type: 'MY_OTHER_EVENT' }, any>;
  }
}

Now I type system.get("myInjectedActor") I get an actor ref with proper types, I know what events can be sent.