Linebreaks between `$$` and label not handled

[darsnack]

The following markdown source:

Some text
$$
y = ax + b
$$
{#eq:my-equation}

will not get picked up by the filter. pandoc-crossref does seem to pick this case up, so perhaps it is fixable here? I'd prefer to use pandoc-xnos because it doesn't insert \hypertarget into the LaTeX.

[KEClaytor]

I'm seeing the same thing using gitlab math blocks;

```math
y = ax + b
\```
{#eq:id}

(had to add the \ to get it to render in the code block