Easy way to add ‘copy to clipboard’ to GitHub markdown?

The copy button is now a reality (May 2021), as tweeted by Nat Friedman

We just added a “Copy” button to all code blocks on GitHub.

To create a copy button, make a Fenced code block as shown here, in a markdown document

```
function test() {
  console.log("This code will have a copy button to the right of it");
}
```