Jekyll创造的：

1. 位于文件头部
2. YAML 格式

Any file that contains a YAML front matter block will be processed by Jekyll as a special file. The front matter must be the first thing in the file and must take the form of valid YAML set between triple-dashed lines. Here is a basic example:

---
layout: post
title: Blogging Like a Hacker
---

refer: https://jekyllrb.com/docs/front-matter/