Add northern pursuit scenario

data/campaign/campaign.json

@@ -88,6 +88,11 @@
       "id": "017_ye_surrender",
       "title": "Ye Surrender",
       "path": "res://data/scenarios/017_ye_surrender.json"
+    },
+    {
+      "id": "018_northern_pursuit",
+      "title": "Northern Pursuit",
+      "path": "res://data/scenarios/018_northern_pursuit.json"
     }
   ]
 }