Add image props documentation for Card component

[devin-ai-integration]

Add image props documentation for Card component

Summary

Added documentation for the Card component's image functionality, which was recently added to the platform. The documentation includes:

• New "Adding images to cards" section with guidance on image usage
• Two interactive examples showing cards with images (left and top positions)
• Complete documentation of all 4 image-related props: src, imagePosition, imageWidth, and imageHeight
• Guidance that imageWidth/imageHeight are optional since images auto-resize by default

Review & Testing Checklist for Human

• Visual verification: View the docs page at /docs/writing-content/components/cards and verify the card image examples render correctly
• Test image URLs: Confirm the Unsplash image URLs display appropriate images and load properly
• Test all positions: Try creating cards with all 4 imagePosition values (top, left, right, bottom) to verify they work as documented - I only showed top and left in examples
• Verify auto-resize behavior: Confirm that images auto-resize appropriately without explicit width/height, and that the optional override props work when specified

Notes

• The Card component implementation was reviewed in fern-platform (commits 69f8e4d6f and 59c8bb2a1) to ensure accuracy of the documentation
• Local docs preview couldn't be fully tested due to an unrelated parsing error in a Java changelog file
• Session: https://app.devin.ai/sessions/c328a6eb54f74fa4b6f156a68095784a
• Requested by: Catherine Deskur (catherine@buildwithfern.com)

[devin-ai-integration]

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[github-actions]

🌿 Preview your docs: https://fern-preview-f104cd5e-62ef-421a-981c-c8b67172ac91.docs.buildwithfern.com/learn

[github-actions]

🌿 Preview your docs: https://fern-preview-11ca63e6-3a54-4431-8882-639f26975a20.docs.buildwithfern.com/learn