```{directive_name} arguments
:option1: name
:option2: other
content...
Input 2:
````markdown
```{directive_name} arguments
:option1: name
:option2: other
content...
Output:
````markdown
```{directive_name} arguments
---
option1: name
option2: other
---
content...
That is, use the YAML-frontmatter-like syntax for consistency and minimized diffs.
Format the fronmatter-like block with a YAML formatter.
Remove redundant initial empty line from content, because the yaml `---` already separates visually.
Format directive options
Input 1: