You can add language links in the sidebar in the new Vector skin again. You do this by connecting the page to a Wikidata item. The new Vector skin has moved the language links but the new language selector cannot add language links yet.
The syntax highlight tool marks up code with different colours. It now can highlight 23 new code languages. Additionally, golang can now be used as an alias for the Go programming language, and a special output mode has been added to show a program's output.