Add Bohai remnants scenario

data/campaign/campaign.json

@@ -103,6 +103,11 @@
       "id": "020_nanpi_surrender",
       "title": "Nanpi Surrender",
       "path": "res://data/scenarios/020_nanpi_surrender.json"
+    },
+    {
+      "id": "021_bohai_remnants",
+      "title": "Bohai Remnants",
+      "path": "res://data/scenarios/021_bohai_remnants.json"
     }
   ]
 }