Move inline JS to static/js/main.js.

[XhmikosR]

We should probably finish #2465, #2462 and look into #2523 before this.

Fixes#2542

Preview: https://elastic-wing-9ce26c.netlify.com/en/

[XhmikosR]

How about we move all JS (maybe not the IE custom modernizr load) to a file named main.js instead of 2 files? I know we have http/2, but these are small files and this way we keep things simple.

[XhmikosR]

I will go with the one file solution. This way we won't have multiple JS files and we won't need to look into concatenating them on build.

I think it's a good compromise given the nature of the project.

[XhmikosR]

Marked it as ready for review.

I only left the IE modernizer check in the HTML. Let me know what you guys think. (Preview #2543 (comment))

PS. I hope no one links to download.js from other Node.js sites. If so, we'll need to rethink this.

[XhmikosR]

I moved everything to main.js. Now the HTML files are free from inline JS.

[Trott]

@nodejs/website This could use some reviews.