[css-writing-modes] Make writing-mode not apply to internal ruby elements

Author: fantasai

css-writing-modes/Overview.bs

@@ -779,7 +779,7 @@ Block Flow Direction: the 'writing-mode' property</h3>
   Name: writing-mode
   Value: horizontal-tb | vertical-rl | vertical-lr | sideways-rl | sideways-lr
   Initial: horizontal-tb
-  Applies to: All elements except table row groups, table column groups, table rows, and table columns
+  Applies to: All elements except table row groups, table column groups, table rows, table columns, ruby base container, ruby text container
   Inherited: yes
   Percentages: n/a
   Media: visual
@@ -2686,6 +2686,8 @@ Full-width Characters</h5>
       Changed the 'caption-side' property to <a href="#logical-direction-layout">flow-relative mappings</a>.
     <li>
       Specified that SVG 'writing-mode' values compute through to new equivalents.
+    <li>
+      Specified that 'writing-mode' does not apply to <a>ruby base containers</a> and <a>ruby text containers</a>
     <li>
       Made several editorial improvements and marked some features <a href="#status">at risk</a>.
   </ul>