Add northern campaign prep milestone

src/game/scenes/TitleScene.ts

@@ -410,7 +410,8 @@ export class TitleScene extends Phaser.Scene {
       campaign.step === 'fifty-fourth-camp' ||
       campaign.step === 'hanzhong-king-camp' ||
       campaign.step === 'shu-han-foundation-camp' ||
-      campaign.step === 'baidi-entrustment-camp'
+      campaign.step === 'baidi-entrustment-camp' ||
+      campaign.step === 'northern-campaign-prep-camp'
     ) {
       this.scene.start('CampScene');
       return;