Support Pandoc syntax in .tex

[koppor]

Follow-up to #57

\documentclass{LNI}
\addbibresource{some.bib}
\let\Bbbk\relax
\usepackage[citations=true]{markdown}
\begin{document}

\begin{markdown}
# Test

[@testkey]

\end{markdown}

\printbibliography

\end{document}

---

@article{testkey,
author = {Hans},
year = 2025
}

---

I think, the plugin should also handle this (in addition to \cite xyz)