vue 组件内引入外部在线js、css

参考：https://blog.csdn.net/u010881899/article/details/80895661

例：引入element-ui

js：

mounted() {
    const oScript = document.createElement(\'script\');
    oScript.type = \'text/javascript\';
    oScript.src = \'https://unpkg.com/element-ui@2.3.7/lib/index.js\';
    document.body.appendChild(oScript);
}

css:

<style scoped>
    @import \'https://unpkg.com/element-ui@2.3.7/lib/theme-chalk/index.css\';
</style>