Work through Jekyll 3 TODOs

[TWiStErRob]

• GHPages:
  • 86-192-228: rouge 1.11.1 -> 2.2.1 -> 3.26.0 https://github.com/rouge-ruby/rouge/blob/master/CHANGELOG.md
  • kramdown 1.13.2 -> 1.17.0 -> 2.3.2
• Jekyll 3.5
  • Sitemaps for static files
  • Liquid 4: https://github.com/Shopify/liquid/blob/main/History.md#400--2016-12-14--branch-4-0-stable
    https://github.com/Shopify/liquid/blob/main/History.md#403--2019-03-12
  • Jekyll now uses Liquid 4, the latest! It comes with whitespace control, new filters concat and compact, loop performance improvements and many fixes
  • Pages, posts, and other documents can now access layout variables via {{ layout }}.
  • The gems key in the _config.yml is now plugins.
  • Filters like sort now allow you to sort based on a subvalue, e.g. {% assign sorted = site.posts | sort: "image.alt_text" %}.
  • layout: null -> layout: none (null = default, none = no layout)
• Jekyll 3.6
  • Rouge 2 support, but note you can continue to use Rouge 1
• Jekyll 3.7
  • --livereload
  • slugify latin
  • collections folder (https://jekyllrb.com/docs/collections/)
  • Ruby 2.5.3
• Jekyll 3.8
  • Ruby 2.7
• Jekyll 3.9
  • allow kramdown v2
    • gem "kramdown-parser-gfm"
    • turn off guessing
  • 3.9.2-3: Ruby 3.0-1-2
• Read news <4 and changelog <4.0
• These two end up in sitemap after update:
  • /dev/assets/css/style.css
  • /dev/redirects.json

dev > sass > line_numbers: true is broken after update (generated CSS files no longer have line numbers)
ref https://github.com/jekyll/jekyll-sass-converter/blob/master/lib/jekyll/converters/scss.rb#L48

dev > sass > sourcemap is disabled, check if it can be enabled

new RegExp('vegetarian is broken in javascript, report backslash issue
contact wasn't working, now it is? (probably should be generated in debug)
shell code formatting lost user@machine$ formatting

https://github.com/jekyll/jekyll/pull/6384/files#diff-514abd885acda367325e5236a9be3192R68
https://github.com/kacperduras/disqus-for-jekyll

[TWiStErRob]

Extracted as separate tickets:

• Enable liquid.strict_variables in _config.yml #33