Fix unclosed angle-bracketed definition
Fix unclosed angle-bracketed definition

The follow is read in commonmark-mode as text:

```md
[bar]: </url
```

Whereas other flavours read the aforementioned as
a definition with a `"link"` property set to
`"</url"`.

Related to https://github.com/eush77/mdast/commit/
ee982ec#commitcomment-15053488.

wooorm/remark,tanzania82/remarks