FEATURE: Site setting for typographic quotation marks

Adds locale defaults for German and French

lib/validators/markdown_typographer_quotation_marks_validator.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class MarkdownTypographerQuotationMarksValidator
+  QUOTE_COUNT = 4
+
+  def initialize(opts = {})
+    @opts = opts
+  end
+
+  def valid_value?(value)
+    value.present? && value.split("|").size == QUOTE_COUNT
+  end
+
+  def error_message
+    I18n.t("site_settings.errors.list_value_count", count: QUOTE_COUNT)
+  end
+end