Put designer wiki doc on the website

Fix absolute links

Add css for details tag

Add installation doc

docs/_plugins/details_block.rb

@@ -0,0 +1,22 @@
+# Mimics an HTML <details> element
+# Courtesy of https://github.com/towbi (https://gist.github.com/towbi/a67fda47e075d2b7fa4764bb42605063)
+class DetailsTag < Liquid::Block
+
+  def initialize(tag_name, markup, tokens)
+    super
+    @caption = markup
+  end
+
+  def render(context)
+    site = context.registers[:site]
+    converter = site.find_converter_instance(::Jekyll::Converters::Markdown)
+    # below Jekyll 3.x use this:
+    # converter = site.getConverterImpl(::Jekyll::Converters::Markdown)
+    caption = converter.convert(@caption).gsub(/<\/?p[^>]*>/, '').chomp
+    body = converter.convert(super(context))
+    "<details><summary>#{caption}</summary>#{body}</details>"
+  end
+
+end
+
+Liquid::Template.register_tag('details', DetailsTag)