New Copycode extension

[schulle4u]

I really like the copy buttons under code examples in documentations and use them quite often, e.g. to copy complex installation commands and ready-to-use configuration on GitHub. As far as I know this feature is not yet available for Yellow, therefore I have built it as a small extension. Copycode automatically adds a copy button to any fenced or indented block of code, which can be used to copy the content of the block to the clipboard. No further configuration is needed for now.

Let me know what you think, any feedback is welcome. 🙂