update: add modifications fee to shipyard

models/Shipyard.json

@@ -32,10 +32,15 @@
       "items": {
         "$ref": "./ShipyardShip.json"
       }
+    },
+    "modificationsFee": {
+      "type": "integer",
+      "description": "The fee to modify a ship at this shipyard. This includes installing or removing modules and mounts on a ship. In the case of mounts, the fee is a flat rate per mount. In the case of modules, the fee is per slot the module occupies."
     }
   },
   "required": [
     "symbol",
-    "shipTypes"
+    "shipTypes",
+    "modificationsFee"
   ]
 }