Markdown link text part parsing not working correctly

[ZaymonFC]

Describe the issue

Link text parts prefixed with www or suffixed with .com/ seem to break the parser.

Repro:

1. Go to https://codemirror.net/5/mode/gfm/index.html
2. Paste the following:

## URL Issues

Leading `www` breaks formatting.
[www.inc.com](https://www.inc.com)

Trailing `.com/` breaks formatting.
[figma.com/](https://www.figma.com)

Ok.
[figma.com](https://www.figma.com)
[any other text](https://www.example.com)

[marijnh]

This is the issue tracker for version 6, but you're linking to the version 5 gfm demo (which shares zero code with version 6). For which version of the library is this issue intended?