Add southern holdouts scenario

data/campaign/campaign.json

@@ -298,6 +298,11 @@
       "id": "059_wu_surrender",
       "title": "Wu Surrender",
       "path": "res://data/scenarios/059_wu_surrender.json"
+    },
+    {
+      "id": "060_southern_holdouts",
+      "title": "Southern Holdouts",
+      "path": "res://data/scenarios/060_southern_holdouts.json"
     }
   ]
 }