1. 添加css
    1. <head>
    2.     <css src="http://externalcss/external.css" src_type="url"/>
    3. </head>
    1. 添加js
    1. <head>
    2.     <script src="http://externaljs/external.js" src_type="url"/>
    3. </head>

    Eg:
    Magento 2 layout插入外部css和js - 图1
    Magento 2 layout插入外部css和js - 图2