Adding copy to clipboard support for highlight code blocks

[djsamperi]

It would be helpful to have support for copy-to-clipboard button for fenced code blocks in
the hugo-book theme. There is a discussion on how to do this here:
https://discourse.gohugo.io/t/copy-to-clipboard-from-code-highlight-context/49633.
I managed to get the simpler (older) strategy working with hugo-book , but
not the one recommended by jmooring that employs Node.js.

[alex-shpak]

Hi!
I looked into adding copy button before, but as I try to keep everything simple I decided against it, it was too much of support for icons, code and light-dark theme,
But I can reconsider is simple (code wise) solution with arise.