add back serve favicon

Author: yyx990803

package.json

@@ -22,6 +22,7 @@
  "html-webpack-plugin": "^2.24.1",
  "lru-cache": "^4.0.1",
  "serialize-javascript": "^1.3.0",
+ "serve-favicon": "^2.3.0",
  "vue": "^2.0.0",
  "vue-router": "^2.0.0",
  "vue-server-renderer": "^2.0.0",