Add Vuex as a dependency.

package.json

@@ -60,6 +60,7 @@
     "vue-loader": "^11.3.4",
     "vue-resource": "^1.3.4",
     "vue-template-compiler": "^2.2.6",
+    "vuex": "^2.3.1",
     "webpack": "^2.6.1",
     "webpack-bundle-analyzer": "^2.8.2"
   },

yarn.lock

@@ -5775,6 +5775,10 @@ vue@^2.2.6:
   version "2.2.6"
   resolved "https://registry.yarnpkg.com/vue/-/vue-2.2.6.tgz#451714b394dd6d4eae7b773c40c2034a59621aed"
 
+vuex@^2.3.1:
+  version "2.3.1"
+  resolved "https://registry.yarnpkg.com/vuex/-/vuex-2.3.1.tgz#cde8e997c1f9957719bc7dea154f9aa691d981a6"
+
 watchpack@^1.3.1:
   version "1.3.1"
   resolved "https://registry.yarnpkg.com/watchpack/-/watchpack-1.3.1.tgz#7d8693907b28ce6013e7f3610aa2a1acf07dad87"