Reference link with newline does not match link reference id

[srawlins]

Take this example:

hello [foo
bar][] there.

[foo bar]: http://x

Most implementations at babelmark (including commonmark) correctly compile this to:

<p>hello <a href="http://x">foo
bar</a> there.</p>

But this package does not match the reference id:

<p>hello [foo
bar ][] there.</p>