Add support for Jekyll-specific filters

[epage]

• [ ] absolute_url
• [ ] markdownify, see https://github.com/cobalt-org/cobalt.rs/issues/342
• [ ] sassify
• [x] slugify
• [ ] jsonify
• [ ] inspect
• [x] where
• [ ] group_by
• [ ] xml_escape
• [ ] uri_escape
• [ ] normalize_whitespace
• [x] sort
• [ ] sample
• [x] push, pop, shift, unshift
• [ ] number_of_words
• [ ] array_to_sentence_string
• [ ] smartify
• [ ] date_to_xmlschema
• [ ] date_to_rfc822
• [ ] date_to_string
• [ ] date_to_longstring

See

• https://jekyllrb.com/docs/templates/
• https://github.com/jekyll/jekyll/tree/master/lib/jekyll/filters.rb
• https://github.com/jekyll/jekyll/tree/master/lib/jekyll/filters
• https://github.com/jekyll/jekyll/blob/master/test/test_filters.rb

[Geobert]

I've encountered prepend, cgi_escape, xml_encode

[Geobert]

I'll take care of slugify soon, need it for my blog