Copy button moves when scrolling in parsed literals

[kai687]

Copy button position on parsed-literal blocks moves when scrolling.

For code blocks, we have a wrapping div.highlight, so the copy button can be positioned against it and stays fixed when the pre block is overflowing.

For pre.literal-block we have no parent wrapping it, so the copy button moves when the pre block is overflowing...

Thanks for the update. I've found a tiny bug, though. If the text is long enough not to fit in the default box, the copy button moves with the code when scrolling.

Originally posted by @KozaMateusz in #2150

[kai687]

@KozaMateusz at the moment I have no idea how to fix this, but I created this issue in case someone has an idea.