Banzai: Add tooltip attributes to reference filter.

lib/banzai/filter/reference_filter.rb

@@ -30,6 +30,8 @@ module Banzai
         attributes = attributes.reject { |_, v| v.nil? }
 
         attributes[:reference_type] ||= self.class.reference_type
+        attributes[:container] ||= 'body'
+        attributes[:placement] ||= 'bottom'
         attributes.delete(:original) if context[:no_original_data]
         attributes.map do |key, value|
           %Q(data-#{key.to_s.dasherize}="#{escape_once(value)}")