Convert images to modern formats (WebP/AVIF)

This helper script uses sharp to convert raster images in the image/ folder into WebP and AVIF images and writes them to image/optimized by default.

Install and run locally:

# from repo root
npm init -y
npm install sharp minimist
node scripts/convert-images.js --src=image --out=image/optimized --formats=webp,avif

Notes:

• AVIF gives better compression but slower conversion; tune quality in the script.
• The script does not modify HTML files. After conversion, update image tags to use <picture> with WebP/AVIF sources and a fallback img pointing to the original.

Example <picture> snippet to replace an <img>:

<picture>
  <source type="image/avif" srcset="/image/optimized/fourier-transform.avif">
  <source type="image/webp" srcset="/image/optimized/fourier-transform.webp">
  <img src="/image/fourier-transform.png" alt="Fourier Transform" class="responsive-img" loading="lazy">
</picture>

If you want, I can prepare automated PR-like patches to replace specific <img> tags with <picture> blocks for a few representative pages; tell me which pages you want converted automatically.