docs: fix broken image URL in vision example

[veeceey]

Summary

• Fixes broken image URL in Vision example that was causing 400 errors
• Replaces large raccoon image (569KB) with smaller, more reliable Danbo cheese image (95KB)
• The previous URL caused download errors when used with the OpenAI API

Changes

• Updated vision example in README.md with working image URL
• New URL: https://upload.wikimedia.org/wikipedia/commons/3/36/Danbo_Cheese.jpg

Testing

• Verified new image URL is accessible (HTTP 200)
• Image is smaller (95KB vs 569KB) which should prevent download issues
• URL format matches OpenAI's vision API requirements

Fixes #2776

[veeceey]

Ready for review and merge. All tests passing.

[karpetrosyan]

Thanks for the PR!
I think it’s more reliable to download the image into the .github folder and then use it via raw.githubcontent.com/PATH

[veeceey]

Thanks @karpetrosyan, that's a good suggestion! I'll download the image into the .github folder and update the reference to use raw.githubusercontent.com. Will push an update shortly.