Is it possible to write back code block backtick count to original?

After #17, #18, code block backtick count is configurable. However, there is another problem.

Now let's consider such senario like below:

ex.) https://github.com/yumetodo/markdown_img_url_editor_rust/blob/master/src/lib.rs#L74

1. Parse markdown file with pulldown-cmark
2. Edit somewhare.
3. Write back to markdown using pulldown-cmark-to-cmark

In this case, there is nothing to emulate block backtick count.

As a result, currently, when just bypass pulldown-cmark to pulldown-cmark-to-cmark, input and output is not equal.