Bracket syntax for links

[Pusnow]

According to spec. There is bracket syntax for links which contain whitespaces.

However, cmark-gfm-swift does not handled it correctly.

input: [link](</my uri>)

cmark-gfm's output: <p><a href="/my%20uri">link</a></p>

cmark-gfm-swift's output: <p>[link](&lt;/my uri&gt;)</p>