[css-logical] Add text-orientation to list of mapping dependencies per css-writing-mode.

Author: fantasai

css-logical-1/Overview.bs

@@ -104,8 +104,9 @@ Introduction</h2>
   <a href="http://www.w3.org/TR/css-writing-modes/">CSS Writing Modes</a>’ <a href="https://www.w3.org/TR/css-writing-modes-3/#abstract-box">Abstract Box Terminology</a> section
   defines how to map between flow-relative and physical terms.
   This mapping,
-  which depends on the <a>used values</a> of 'writing-mode' and 'direction',
-  controls the interpretation of flow-relative keywords and properties.
+  which depends on the <a>used values</a> of
+  'writing-mode', 'direction', and 'text-orientation',
+  controls the interpretation of [=flow-relative=] keywords and properties.
 
   <div id="mapping-diagram">
     <figure>