Add VHEA table to ascend descent OT note for vertical text

Author: fantasai

css3-writing-modes/Overview.html

@@ -1182,9 +1182,10 @@ <h4 id=opentype-baselines><span class=secno>4.2.1. </span> Baselines in
    font's OS/2 table. These should match the <var>idtp</var> and
    <var>ideo</var> baselines (respectively), which, if present, may be used
    instead. In the absence of these metrics, the <var>Ascent</var> and
-   <var>Descent</var> metrics from the HHEA table should be used. The Win
-   metrics can be used as a fallback; however these are intended as clipping
-   bounds and are not always appropriate for use as em box measurements.
+   <var>Descent</var> metrics from the HHEA/VHEA table should be used. The
+   Win metrics can be used as a fallback; however these are intended as
+   clipping bounds and are not always appropriate for use as em box
+   measurements.
 
   <h3 id=replaced-baselines><span class=secno>4.3. </span> Atomic Inline
    Baselines</h3>

css3-writing-modes/Overview.src.html

@@ -848,7 +848,7 @@ <h4 id="opentype-baselines">
     font's OS/2 table. These should match the <var>idtp</var> and <var>ideo</var>
     baselines (respectively), which, if present, may be used instead. In the
     absence of these metrics, the <var>Ascent</var> and <var>Descent</var>
-    metrics from the HHEA table should be used. The Win metrics can be
+    metrics from the HHEA/VHEA table should be used. The Win metrics can be
     used as a fallback; however these are intended as clipping bounds and
     are not always appropriate for use as em box measurements.</em>