Add error code

Author: markerikson

errors.json

@@ -37,5 +37,6 @@
   "35": "Cannot use `create.asyncThunk` in the built-in `createSlice`. Use `buildCreateSlice({ creators: { asyncThunk: asyncThunkCreator } })` to create a customised version of `createSlice`.",
   "36": "`context.addCase` cannot be called with an empty action type",
   "37": "`context.addCase` cannot be called with two reducers for the same action type: type",
-  "38": "No insert provided for key not already in map"
+  "38": "No insert provided for key not already in map",
+  "39": "\\`builder.addCase\\` cannot be called with two reducers for the same action type ''"
 }