Add highlightjs support

[ErikSchierboom]

Exercism uses highlightjs for syntax highlighting. Unfortunately, there is no support for this track at the moment (see the supported languages).

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 exercism/v3-launch#36

[joshgoebel]

Let me know if I can help.

We could probably use lisp or clojure until there is a Shen grammar. Perhaps that's enough depending on how lisp-like Shen is...

[jaccarmac]

Depending on how type-heavy the code is, I think Clojure highlighting gives decent results. Rendering a file from the Shen source distribution in each mode and seeing how it looks would be a good next step.

[ErikSchierboom]

PR created: #46