主题开发最的基本要素：name, type, core，例子<code>demo.info.yml</code>：
```
name: Demo theme
description: Drupal 8 demo theme
type: theme
core: 8.x
```
drupal资料主题素材源：
C:\wamp64\www\drupal_dev\drupal869\core\modules\system\templates
<br/>
更换css, js, images链接：
```
"css/
<!-- 转换为 -->
"themes/demo1/css/
```
free bootstrap template:
https://github.com/BlackrockDigital/startbootstrap-modern-business
