(hotfix): actually make localStorage the default

- I thought I made this edit before but I guess I forgot to add it in
  - maybe I looked at https://github.com/pinqy520/mobx-persist/blob/a0bb0ea26142c498665dc65a096acab46c21847f/src/index.ts#L41
    and thought the code was okay -- but it's also set to the default
    arg a few lines up

persist.js

@@ -5,7 +5,7 @@ import * as LocalStorage from './localStorageAdaptor.js'
 export const persist = (name, store, options = {}) => {
   let {storage, jsonify, whitelist, blacklist} = options
 
-  if (typeof window.localStorage !== 'undefined' && window.localStorage === storage) {
+  if (typeof window.localStorage !== 'undefined' && (!storage || storage === window.localStorage)) {
     storage = LocalStorage
   }
   if (!jsonify) { jsonify = true } // default to true like mobx-persist