Improve markdown support and tweak sponsorship langage

app/helpers/format_helper.rb

@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+require 'redcarpet/render_strip'
 
 module FormatHelper
   ##
@@ -206,6 +207,11 @@ module FormatHelper
     markdown("#{text} Please look at #{link_to '**Markdown Syntax**', 'https://daringfireball.net/projects/markdown/syntax', target: '_blank'} to format your text", false)
   end
 
+  # Return a plain text markdown stripped of formatting.
+  def plain_text(content)
+    Redcarpet::Markdown.new(Redcarpet::Render::StripDown).render(content)
+  end
+
   def quantity_left_of(resource)
     return '-/-' if resource.quantity.blank?