DocGen Copy button for code snippets

[juancarlospaco]

Would be great to add a "Copy" button to the code blocks rendered by the Docgen,
just like GitHub itself has nowadays on the code blocks, the Docgen needs to add 1 line:

<button onclick="document.querySelector('#SELECTOR').select();document.execCommand('copy');">Copy</button>

What do you think of the idea @a-mr ?.

...and thanks for all the awesome work on the docgen!. 🙂