Markdown files with CR LF line endings instead of LF do not create mermaid output

[pseiko1989]

Markdown files with CR-LF line endings will only create an empty

<pre class="mermaid">
</pre>

instead of the code block.

It should be possible to verify it with the following files: test_cr_lf.md test_lf.md

The cause of this may be that events.into_offset_iter() in https://github.com/badboy/mdbook-mermaid/blob/main/src/lib.rs#L64 returns the mermaid content line by line instead of in one big chunk.

[badboy]

PRs welcome. I don't have CRLF line endings, so I'm not too eager to investigate this right now.