Update download page URL to match selected languages

Upgrading the library is difficult when we’ve selected extra languages in the download page, as there’s no good way of downloading the same bundle in the future.

Prism.js solves this by updating the URL to match the selected checkboxes, and embedding that URL in the resulting download as a comment. See https://prismjs.com/download.html#themes=prism-okaidia&languages=markup+css+clike+javascript, which includes markup, css, clike, and javascript. Having such a feature on our downloads page would be really wonderful.

Similar to #1035

[tammersaleh]

Just a quick further comment. I think after https://github.com/highlightjs/highlight.js/issues/1035, y’all added a cookie-based approach that saved the current checkboxes. That really doesn’t work when the cookies get deleted or the project is team-wide. Having a URL is much better, especially if it’s embedded in the downloadable in some way.

[joshgoebel]

Would you prefer having a cURL option?

Didn’t they answer that already: 😉

I’d probably use a curl-based approach if it existed, but it’d be a nice-to-have.