example(vuex-store): change to module store (#4923)

examples/vuex-store/store/index.js

@@ -1,14 +1,9 @@
-import Vuex from 'vuex'
+export const state = () => ({
+  counter: 0
+})
 
-import mutations from './mutations'
-
-const createStore = () => {
-  return new Vuex.Store({
-    state: {
-      counter: 0
-    },
-    mutations
-  })
+export const mutations = {
+  increment(state) {
+    state.counter++
+  }
 }
-
-export default createStore

examples/vuex-store/store/mutations.js

@@ -1,7 +0,0 @@
-const mutations = {
-  increment(state) {
-    state.counter++
-  }
-}
-
-export default mutations