add linkref for LaTeX

_includes/links.md

@@ -69,6 +69,7 @@
 [jupyter-nbdime]: https://github.com/jupyter/nbdime
 [jupyter]: https://jupyter.org/
 [kramdown]: https://kramdown.gettalong.org/
+[latex]: https://www.latex-project.org/
 [lc-lessons]: https://librarycarpentry.org/lessons/
 [lesson-aio]: {{ relative_root_path }}{% link aio.md %}
 [lesson-coc]: {{ relative_root_path }}{% link CODE_OF_CONDUCT.md %}