Wrongly setting syntax by VIM modelines in Markdown code block

[jfcherng]

This is a Markdown file but ASS sets it to YAML because there is # vim: set ft=yaml: in the code block.

file.md

## File.md

Here's a YAML example.

```yaml
# vim: set ft=yaml:
# ^^^^^^^^^^^^^^^^^ the above line make ASS set syntax to YAML

key: value
```