Update highlight.js to support Solidity

[pepuscz]

I see that highlight.js supports Solidity (https://github.com/highlightjs/highlight.js/blob/main/SUPPORTED_LANGUAGES.md) but it's not selectable in Code Blocks.

Can you please check why it's not working?

[pash7ka]

I guess that's because highlight.js does not support Solidity natively, but via highlightjs-solidity package.

I would love to have Solidity supported. If needed, i can make a PR adding it ( i guess i will need to add the highlightjs-solidity to package.json and to the client/sidebar.js)