Add lazy loading of images in Jekyll posts
note, Nov 5, 2023, on Mitja Felicijan's blog
Normally you define images with ![]() in markdown files. But jekyll also
provides a way to adding custom attributes to tags with {:attr="value"}.
If you have lots of posts this command will append `` to all
images in all your markdown files.

will become

Shell line bellow. Go into the folder where your posts are (probably _posts).
find . -type f -name "*.md" -exec sed -i -E 's/(\!\[.*\]\((.*?)\))$/\1/' {} \;
Under the hood this adds loading="lazy" to HTML img nodes.
That is about it.