Dynamically generate share images

[Snugug]

Instead of just a generic share images, we should dynamically generate share images that include some information about the page, similar to what GitHub does with repos.

Maybe utilize something like https://vercel.com/blog/introducing-vercel-og-image-generation-fast-dynamic-social-card-images

[Snugug]

This is becoming more important as the images being grabbed seem to be fairly random and, in some cases, aren't what we want at all (author headshot, for instance).

May be blocked on withastro/roadmap#916, but then we should be able to use https://www.npmjs.com/package/@vercel/og to render, something:

• https://www.kozhuhds.com/blog/generating-static-open-graph-og-images-in-astro-using-vercel-og/
• Container APIs withastro/roadmap#916 (comment)