jekyll keep image aspect-ratio to avoid CLS

fix_img_dimensions.rb

# Initially generated by LLM
# Put in _plugins/ and add fastimage and nokogiri to deps
require 'fastimage'
require 'nokogiri'

Jekyll::Hooks.register %i[pages posts], :post_render do |page|
  next unless page.output_ext == '.html'

  doc  = Nokogiri::HTML5.parse(page.output)
  changed = false

  doc.css('img:not([height])').each do |img|
    src = img['src']
    next if src.nil? || src =~ %r{^https?://}

    path = File.join(page.site.source, src)
    next unless File.exist?(path)

    w, h = FastImage.size(path)
    next unless w && h

    img['style']   = [img['style'], "aspect-ratio:#{w}/#{h};"].compact.join
    changed = true
  end

  page.output = doc.to_html if changed
end