feat: Add highlight JS

[ahmedsaheed]

This add supports of code block highlighting via markdown-it-highlightjs.
It should also close post by @mb21 in mb21/panwriter#96 (comment)

[mb21]

Thanks for the pull request! Seems you run an auto-formatter over the code, was it Prettier? I'm not opposed to doing that, but would be great if it's a separate commit, otherwise it's hard to see what else was changed.

[ahmedsaheed]

Yes, ran prettier over the code. But the main change is in the second commit

[mb21]

The second commit simply adds , {auto: true}? But whatever, if it's well tested, I can add it quickly myself if that's okay for you as well...