feat(account-tree-controller): add missing stateChange event to AccountTreeControllerEvents (#5958)

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## Checklist

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Author: PatrykLucka

packages/account-tree-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Add `AccountTreeControllerStateChangeEvent` to `AccountTreeControllerEvents` ([#5958](https://github.com/MetaMask/core/pull/5958))
+
 ## [0.1.0]
 
 ### Added

packages/account-tree-controller/src/AccountTreeController.ts

@@ -101,7 +101,7 @@ export type AllowedEvents =
   | AccountsControllerAccountAddedEvent
   | AccountsControllerAccountRemovedEvent;
 
-export type AccountTreeControllerEvents = never;
+export type AccountTreeControllerEvents = AccountTreeControllerStateChangeEvent;
 
 export type AccountTreeControllerMessenger = RestrictedMessenger<
   typeof controllerName,