Codidact uses highlight.js for syntax highlighting. We support whatever languages are enabled by default in that package; we haven't restricted them. As I write this, they list 189 languages with examples on their website as well as on a table on their GitHub.
Syntax highlighting is enabled for communities that request it, but not everywhere. (That's why your attempts to provide an example didn't work here on Meta.) We do this because, like Mathjax, syntax highlighting adds some rendering time to every post, and we don't want to slow down sites that wouldn't benefit.
When highlighting (or Mathjax) is enabled for a community, it's enabled for all categories, including meta.