Website documentation improvement

[erfanatp]

Congratulations for the new version of Tailwind CSS.

I have a suggestion for improvement in the colors section. I can contribute by making the color class names copyable to the clipboard when clicking on the color squares. For example, clicking on a square would copy "red-400" or "slate-800" to the clipboard.

I hope this helps!

[wongjn]

The repo for the docs site is at https://github.com/tailwindlabs/tailwindcss.com if you wanted to make a PR