fix: emit og:image instead of og:image:url for images array

[nureddinhaji]

Problem

The images handler in open-graph.svelte emits og:image:url instead of bare og:image for the url key. Without the root og:image tag, most social platforms (Facebook, LinkedIn, Twitter/X, Discord, Slack) do not pick up the image.

The videos handler already correctly special-cases url to emit og:video, but the images handler was missing this same logic — a copy-paste inconsistency.

Fix

Mirror the videos pattern: when imgKey === "url", emit og:image instead of og:image:url.

{@const prop = imgKey === "url" ? "og:image" : \`og:image:\${imgKey}\`}

One line changed.

References

• OG spec on structured properties: https://ogp.me/#structured
• The spec's own examples always use bare og:image, not og:image:url alone
• og:image is listed as one of the four required basic metadata properties

Tests

Updated the existing test to assert og:image instead of og:image:url. All 81 tests pass.