HTML comment that contains @ causes stray "–>" in output

[amartini51]

Description

Input like the following causes the issue:

Hi there.

<!--
  @test
-->

In contrast, this renders correctly:

Hi there.

<!--
  test
-->

It seems like DocC is trying to parse an @ directive block in the middle of the comment.

Checklist

• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue.

rdar://101144032

[ethan-kusters]

@QuietMisdreavus should we transfer this to swift-markdown?

[QuietMisdreavus]

Yes please! The bug would be solved there. I'll do the transfer.

[QuietMisdreavus]

There's a known issue (rdar://98695544) about block directives closing off any other container they're in (block quotes, lists, etc), but this seems like it would be solved differently. I'm not sure if cmark-gfm differentiates between an HTML comment or just any other kind of HTML block, but if we can tell we're in a comment we shouldn't parse directives in the first place. If all we know is that we're in an HTML block, we should solve the other issue with block directives, which would also solve this one.