Explore hosting an optimising image proxy alongside nginx

[PeterJCLaw]

Since we pull together the various parts of our website behind a single proxy machine anyway we could perhaps make that proxy also resize & optimise the images served to users. This would avoid needing to do this quite so aggressively in the source repos (we'd still want to e.g: optimise the file sizes, but wouldn't need to down-scale or reduce quality), while still delivering highly optimised images to users.

https://github.com/imgproxy/imgproxy/ is an example I've used before and isn't too hard to deploy.

[PeterJCLaw]

Note: since we're now using GitHub Actions to publish all our sites we now have more options to do e.g: image optimisation at build time. That may make this approach less appealing.