docs(rendering): hide light image in dark mode

[mst101]

🔗 Linked issue

❓ Type of change

• [ x] 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

The page at https://nuxt.com/docs/guide/concepts/rendering shows both light and dark versions of the images. I don't know how to conditionally render an image from within markdown(?), but this PR at least hides the light version of the image when dark mode is set by simply adding a tailwind class of dark:hidden.

N.B. I'm not sure what the current classes of .light-img and .dark-img currently do, if anything?

📝 Checklist

• I have linked an issue or discussion.
• [ x] I have updated the documentation accordingly.

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[vercel]

@mst101 is attempting to deploy a commit to the Nuxt Team on Vercel.

A member of the Team first needs to authorize it.

[danielroe]

Thanks! ❤️

cc: @clemcode