Only show the copy button when hovering

[tomasr8]

(Reported by @StanFromIreland on Discord)

The new copy button can sometimes cover part of the source code:
https://docs.python.org/dev/library/string.html#format-examples

We can fix this by making the copy button appear only when hovered.

Please don't pick up this issue, I'd like to reserve it for someone at the PyConUS sprints :)

[StanFromIreland]

Please don't pick up this issue, I'd like to reserve it for someone at the PyConUS sprints :)

You should probably add it to the project, I doubt many will check this issue tracker.

[encukou]

Please keep it possible to copy from a touchscreen.
It might be better to add padding-right, so users can scroll past the button.

[StanFromIreland]

It might be better to add padding-right, so users can scroll past the button.

That would be good, but to indicate there is text behind it making it somewhat transparent too would be nice IMO.

[tomasr8]

Please keep it possible to copy from a touchscreen. It might be better to add padding-right, so users can scroll past the button.

The example given on discord (https://pradyunsg.me/furo/kitchen-sink/blocks/#literal-blocks) allows that by first tapping on the codeblock (probably some :active/:focus CSS rule) which I think is also fine, but a padding would work too

[kevteg]

I'm taking a look

[kevteg]

I fixed the issue in this PR. I decided to go with the hover approach, I think it looks better than the padding-right