Switch to chroma for code syntax highlighting

[jbub]

• Drop support for https://highlightjs.org/
• https://gohugo.io/content-management/syntax-highlighting/

[kandelvijaya]

I think this is much needed. I have hard time configuring highlight.js.

[mthmulders]

Is there anything I could do to help on this issue? I see there's already a PR (thanks, @SteveLane!) so doing another one probably doesn't make sense... ;-)

[jbub]

Hey all, i have recently started working on this one, i want to make the transition as backwards compatible as possible :)

[geongeorge]

Can someone help me how to manually switch to chroma?