Use the largest thumbnail size in the resource meta file.

[funkydunc]

Made extract-copy-local.js which is a local copy of extract-thumbnail.js from headless-static-site.
Tweaked this to request the thumbnail closest to 1080x1080 (recommended for og:image), with a fallback of 256x256 which is what was previously used to populate the meta file.

Exhibition
<meta property="og:image" content="https://dlc.services/thumbs/7/24/14204410-74cc-5796-04f2-a59eeaa8ab44/full/1024,/0/default.jpg"/><meta property="og:image:width" content="1024"/><meta property="og:image:height" content="563"/>

Object
<meta property="og:image" content="https://dlc.services/thumbs/7/18/4045ba8b-2160-40b4-9a4b-ae2235280f3d/full/1024,/0/default.jpg"/><meta property="og:image:width" content="1024"/><meta property="og:image:height" content="683"/>

Publication
<meta property="og:image" content="https://dlc.services/thumbs/7/21/b65dbfcc-4daf-0b7d-86fc-74a126248b03/full/full/0/default.jpg"/><meta property="og:image:width" content="1080"/>

[github-actions]

Netlify output

Static site (preview): https://deploy-preview-35--heritage-tudelft.netlify.app
IIIF (preview): https://deploy-preview-35--delft-iiif.netlify.app
IIIF Collection (preview): Theseus

[sammeltassen]

Neat! This works really well (now previews appear when sharing on iMessage and Whatsapp; the previous thumb was too small). Not sure if this is related to this PR but the url tags starts with http://localhost:3000/....

[funkydunc]

Not sure if this is related to this PR but the url tags starts with http://localhost:3000/....

This is resolved now (It was an incorrect environment variable used for the metadata base url)