Move event handler functions to types [ci minor]

src/@types/index.ts

@@ -1,4 +1,5 @@
-export type { GameEngine } from '../GameEngine';
+import type { GameEngine } from '../GameEngine';
+export type { GameEngine };
 
 export type Player = Record<string, unknown> & { id: string | number };
 
@@ -22,3 +23,11 @@ export interface Event<T = unknown> {
 export type HistoryItem = {
   timestamp: Date;
 } & ({ event: Event } | { achievement: Achievement });
+
+export type AchievementAchievedListener = (
+  player: Player,
+  achievement: Achievement,
+  engine: GameEngine
+) => void;
+
+export type EventOccurredListener = (player: Player, event: Event, engine: GameEngine) => void;

src/GameEngine.ts

@@ -10,7 +10,15 @@
  * The GameEngine is an `EventEmitter`, emitting events when an
  * event has occured or an achievement has been achieved.
  */
-import type { Achievement, Event, GamePlayer, HistoryItem, Player } from './@types';
+import type {
+  Achievement,
+  AchievementAchievedListener,
+  Event,
+  EventOccurredListener,
+  GamePlayer,
+  HistoryItem,
+  Player,
+} from './@types';
 import { AchievementRule } from './AchievementRule';
 import { DataStore } from './DataStore';
 import { MemoryDataStore } from './MemoryDataStore';
@@ -34,12 +42,6 @@ interface GameEngineProps {
 
 type GAME_ENGINE_ACHIEVEMENT_ACHIEVED = 'achievement-achieved';
 type GAME_ENGINE_EVENT_OCCURRED = 'event-occurred';
-type AchievementAchievedListener = (
-  player: Player,
-  achievement: Achievement,
-  engine: GameEngine
-) => void;
-type EventOccurredListener = (player: Player, event: Event, engine: GameEngine) => void;
 
 export class GameEngine extends EventEmitter {
   /**