[css-ruby-1] Suggest that UA's scale down font minimums on ruby annotations per <https://lists.w3.org/Archives/Public/www-style/2015Sep/0001.html>

Author: fantasai

css-ruby-1/Overview.bs

@@ -1518,6 +1518,9 @@ Appendix A: Default Style Sheet</h2>
 	Note: Authors should not use the above rules:
 	a UA that supports ruby layout should provide these by default.
 
+	UAs implementing a user-controlled “minimum font size” feature
+	should consider scaling that minimum down for ruby annotations.
+
 <h3 id="default-inline" class="no-num">
 <span class="secno">A.2</span> Inlining Ruby Annotations</h3>