Code fencing is a function of the markdown parser, so probably a no go. You can search the forums, there was talk of replacing BlackFriday with a new parser, and maybe it has other options.
This is implemented as a rendering hook in Hugo, so It should be possible to make up some syntax, e.g. “```js/hl_lines=8-13”. But it’s not a “planned feature”, but it would be useful.
Note that it is on the TODO list to add support for Goldmark, which may or may not make this simpler. It’s probably at least worth looking at that before implementing above so we’re not getting shot in the foot.