References stop working after backticks used in link text

A similar problem to #134 occurs after backticks have been used within a link text.

Code:

`Picture` object: A
[`tikzpicture` environment](https://pgf-tikz.github.io/pgf/pgfmanual.pdf#subsubsection.12.2.1)
is represented by a `Picture` object.

Result:

The `Picture` before the explicit link is automatically linked to the description of that class, but after the backticks in the text of the explicit link, it just becomes a normal code span. This effect persists until the end of the respective docstring, across paragraph boundaries.

I suspect regular expressions are not sufficient to parse Markdown syntax.

A workaround is to use html <code> tags in the link text:

`Picture` object: A
[<code>tikzpicture</code> environment](https://pgf-tikz.github.io/pgf/pgfmanual.pdf#subsubsection.12.2.1)
is represented by a `Picture` object.

Start by reproducing the supplied docstring example with backticks inside explicit link text and inspect the Markdown and reference-link parsing entry points. Done means references after such a link remain linked correctly across paragraph boundaries, while the link text still renders as code.