Jekyll plugin that adds loading="lazy" to all images?

Question

Is there a way to intercept the generating of Jekyll via Jekyll::Generate and add the lazing loading element to all IMGs?

I've got this but it seems the variable that holds the content at this point is frozen (Error: can't modify frozen string)

module Jekyll
  class LazyLoadImagesGenerator < Jekyll::Generator
    def generate(site)
      site.pages.each do |page|
        page.content = lazy_load_images(page.content)
      end

      site.posts.docs.each do |post|
        next if post.data["layout"] == "none" # Skip posts with "none" layout
        post.content = lazy_load_images(post.content)
      end
    end

    def lazy_load_images(content)
      content.gsub!(/(<img[^>]+)(?<!loading="lazy")>/i, '\1 loading="lazy">')
    end
  end
end