Fix copy to clipboard functionality

[coolharsh55]

The existing copy functionality that creates a copy button and handles onclick copy to clipboard does not work as intended (checked on multiple browsers).

prefix.cc/script.js

Line 82 in cbc85c0

function setUpCopyButtons() {

I'm not sure exactly what doesn't work (though there's old crud there e.g. flash code). Might be a good idea to move to newer clipboard APIs e.g. Clipboard.write()