* refactor svg

* add svgo

* refine

* add tree.svg

* add svg.yml

https://github.com/sindresorhus/screenfull.js/pull/111

detail see https://panjiachen.github.io/vue-element-admin-site/#/zh-cn/lazy-loading?id=%E8%B7%AF%E7%94%B1%E6%87%92%E5%8A%A0%E8%BD%BD

The vue-loader build error caused by Prettier have been fixed

detail see #534

* update element-ui && refactor sidebar.css

* format

* bump deps: update vue-splitpane version

* refactor[chore]: use webpack-dev-serve build

* perf:settings

* doc: uodate readme