Some common programming languages don't show up for autocompletion, others don't work at all

For example Java doesn't show up for autocompletion, and C or C++ don't seem to work at all.
Personally, I'd also love to see Haxe, which highlight.js does support.

Would it be possible for people hosting their own hackmd instances to download or link their own highlight.js packages?

Start by tracing the language autocompletion and highlight.js integration described in the issue; no specific files or tests are named. Check how Java, C, and C++ are registered and how self-hosted instances load highlight.js packages. Done means those languages work, Haxe is available if supported, and hosts can provide their own package.

Vom Indexierungsmodell aus dem Issue-Text verfasst.