Add copy lint name function to Clippy's lint list

[xFrednet]

I often want to copy the lint name when searching for something on Clippy's lint list. It would be helpful to have a "copy lint name"-button next to the name, similar to the "link"-button that currently exist.

The current "link"-button looks like this:

The HTML document of the page can be found under util/gh-pages/index.html. cargo dev serve can be used to test the changes locally.

Main tracking issue #7172

[Mastermindaxe]

I'll take this if no one minds