[Request] Support code block in lists

[ben-grande]

Hi, code blocks can indented on the same level as the list item. I think it would be valuable to support them.

File ex.md:

# Title

* List with code block:

  ```sh
  echo hi
  ```

presenterm ex.md

                    Error loading presentation:

                    parse error at 5:3: unsupported
                    structure in list: code block