don't check URLs inside brackets in markdown

[anarcat]

Harper flagged this as an error:

<http://localhost:9093>

"Did you mean to spell “localhost” this way?"

Yes, I did. In fact, I meant http://localhost:9093. I can work around that with:

`http://localhost:9093`

... but it's really not the same, as it's not clickable.

[chrisgrieser]

related: #104

[elijah-potter]

@grantlemons, will this be fixed by #305?

[grantlemons]

I think so, but #305 needs some work since it's very out of date at this point.

This should be because the <link> syntax uses the link itself as the displayed text, so it is spellchecked, which is something configurable under #305.