reintroduce InitializeGame in boardgame.io/core

Author: nicolodavis

packages/core.js

@@ -6,13 +6,17 @@
  * https://opensource.org/licenses/MIT.
  */
 
-import { INVALID_MOVE } from '../src/core/reducer.js';
-import {
-  Pass,
+import { INVALID_MOVE } from '../src/core/reducer';
+import { Pass, ActivePlayers, TurnOrder, Stage } from '../src/core/turn-order';
+import { InitializeGame } from '../src/core/initialize';
+import { PlayerView } from '../src/core/player-view';
+
+export {
   ActivePlayers,
-  TurnOrder,
   Stage,
-} from '../src/core/turn-order.js';
-import { PlayerView } from '../src/core/player-view.js';
-
-export { ActivePlayers, Stage, TurnOrder, Pass, PlayerView, INVALID_MOVE };
+  TurnOrder,
+  Pass,
+  PlayerView,
+  InitializeGame,
+  INVALID_MOVE,
+};