类 Setext 形式是用底线的形式,利用 = (最高阶标题)和 - (第二阶标题),例如:
This is an H1 ======= ====== This is an H2 ----------- ---------------
六个点
This is an H1
==========
This is an H2
---------------------
每一行都加缩进
This is an H1
==========
This is an H2
---------------------