Support build caching / not rebuilding images if they already exist?

[JoshuaKGoldberg]

Coming over from flint-fyi/flint#1781 (comment): I'm seeing astro-og-canvas:

• Rebuilds images even if they already exist in the output og/ directory
• Runs a lot slower in GitHub Actions CI (guessing: for lack of fancy Mac M# chips / GPUs)

Combined, that's resulting in the repo's builds taking an extra 15+ seconds in CI to rebuild a little under 100 images (~170ms/image average). Once our repo gets up to its projected ~1000 images by the end of 2025, that'll be ~5 minutes in CI for every build.

Proposal: could astro-og-canvas have some kind of caching feature? For example, could it keep a hash/registry on disk of images to be built, and only (re)build images when there is a missing cache or mismatch?

(alternately, if there's a more Astro-native solution we should be using, I'd love to know! and maybe add that to docs here?)

[delucis]

This should already be the case! It uses the same caching strategy Astro itself does so if you’re caching node_modules it should work! (Added this pretty quickly because otherwise Astro’s docs would take 15 minutes for every build 😅)