Unselectable prompt for code blocks

[zmoon]

Proposal

So you can write something like

$ cd mystmd

but the prompt (here $ ) isn't included when you select text or use the copy button. Like enabled by the sphinx-prompt Sphinx extension. But I wonder if this could be accomplished with options for the existing code/code-cell directives instead of a new directive.

```{code} bash
:prompt: $

$ cd mystmd
```

[parmentelat]

I'd love this one maybe being able to somehow configure a default language-to-prompt map globally could help reduce the overhead :)