Add highlightjs support

Exercism uses [highlightjs](https://highlightjs.org/) for syntax highlighting. Unfortunately, there is no support for this track at the moment (see the [supported languages](https://github.com/highlightjs/highlight.js/blob/main/SUPPORTED_LANGUAGES.md)).

To properly support syntax highlighting for this track, an official grammar should be created at https://github.com/highlightjs/highlight.js/tree/main/src/languages. Note that this grammar could be relatively minimal at first and can be expanded upon at a later time.

@joshgoebel has initimate knowledge of the code base and has graciously offered to be available for any questions.

See https://github.com/exercism/v3-launch/issues/36