Widget on block of code to copy the code to your clipboard

On my site – https://www.sharons.org.uk – I have several postings with large blocks of code. How can I get it so that You just click on the top-right of the block of code and its copied to your clipboard so you can paste it and use it in your site, please? I don’t know if it can be done with a plugin or whether its some form of code to be pasted into the css, or whatever? All my searches for a plugin have been unsuccessful, unfortunately.

Thanks
Sharon.