Highlight.js changed their default branch from master to main. This switches to the @highlightjs/cdn-assets package, thus sidestepping the problem. It's a slightly cleaner integration though (no need to build locally anymore).
Moves Highlight.js files to vendor/assets/javascripts
Adds Highlight.js in yarn package management
Removes old rake task and reliance on NPM to build Highlight.js
Highlight.js is now integrated in the "javascript:update" rake task
