Add docs recipe for buildImageUrl() sizes and formats

[TDanks2000]

Background

The package exports buildImageUrl(imageId, options) and the IGDB_IMAGE_SIZES list. The README and examples show a cover URL, but a focused recipe would help new users choose sizes, retina variants, and file extensions without reading the source.

Proposed change

Add a small recipe that demonstrates cover_big, screenshot_big, retina: true, and the jpg / png / webp extension option.

Acceptance criteria

• Shows at least three buildImageUrl() calls using real exported options.
• Mentions that the helper expects an IGDB image ID, not a full image URL.
• Links to or mentions IGDB_IMAGE_SIZES.
• Does not introduce unsupported image sizes.

Files likely involved

• docs/examples.md
• docs/api-reference.md
• src/utils/images.ts