Improve code snippets style

[jcubic]

This is how code snippets looks like in output files:

And this is how it looks like on the original website:

So the main task is to add the same box (only colors and rounded corners) that will work on light and dark mode.

[Macvncpro]

Hi,

I would like to give this a go, just to confirm are these changes only to the colour and round corners?

Thanks.

[jcubic]

Yes, but I think there are already rounded corners.