Adjust radio button size based on number of answer options

app/views/form/_radio_question.html.erb

@@ -1,6 +1,7 @@
 <%= f.govuk_radio_buttons_fieldset question_key,
     legend: { text: question["header"], size: "l" },
-    hint: { text: question["hint_text"] } do %>
+    hint: { text: question["hint_text"] },
+    small: (question["answer_options"].size > 5) do %>
 
     <% question["answer_options"].map do |key, val| %>
       <% if key.starts_with?("divider") %>