Add changeset for core

.changeset/bright-zoos-reflect.md

@@ -0,0 +1,38 @@
+---
+'xstate': minor
+---
+
+Spawned/invoked actors and interpreters are now typed as extending `ActorRef` (e.g., `SpawnedActorRef`) rather than `Actor` or `Interpreter`. This unification of types should make it more straightforward to provide actor types:
+
+```diff
+import {
+- Actor
++ ActorRef
+} from 'xstate';
+
+// ...
+
+interface SomeContext {
+- server?: Actor;
++ server?: ActorRef<ServerEvent>;
+}
+```
+
+It's also easier to specify the type of a spawned/invoked machine with `ActorRefFrom`:
+
+```diff
+import {
+  createMachine,
+- Actor
++ ActorRefFrom
+} from 'xstate';
+
+const serverMachine = createMachine<ServerContext, ServerEvent>({
+  // ...
+});
+
+interface SomeContext {
+- server?: Actor; // difficult to type
++ server?: ActorRefFrom<typeof serverMachine>;
+}
+```