Update stylesheets order doc

Author: JayPanoz

docs/CSS06-stylesheets_order.md

@@ -62,6 +62,7 @@ The following modules must be appended after the author’s stylesheets (`Readiu
     10. `ReadiumCSS-paraSpacing_pref.css` (or `ReadiumCSS-paraSpacing-vertical_pref.css` for CJK – vertical writing mode)
     11. `ReadiumCSS-paraIndent_pref.css` (does not apply to CJK scripts)
     12. `ReadiumCSS-wordSpacing_pref.css` (does not apply to RTL and CJK scripts)
-    13. `ReadiumCSS-letterSpacing_pref.css` (does not apply to RTL and CJK scripts)
+    13. `ReadiumCSS-letterSpacing_pref.css` (does not apply to RTL scripts, except in vertical writing mode)
     14. `ReadiumCSS-arabicLigatures_pref.css` (RTL only)
+    15. `ReadiumCSS-ruby_pref.css` (CJK only)
 8. `ReadiumCSS-fs_normalize.css`

docs/ReadiumCSS_docs.epub

@@ -118,9 +118,11 @@
 
           <li><code>ReadiumCSS-wordSpacing_pref.css</code> (does not apply to RTL and CJK scripts)</li>
 
-          <li><code>ReadiumCSS-letterSpacing_pref.css</code> (does not apply to RTL and CJK scripts)</li>
+          <li><code>ReadiumCSS-letterSpacing_pref.css</code> (does not apply to RTL scripts, except in vertical writing mode)</li>
 
           <li><code>ReadiumCSS-arabicLigatures_pref.css</code> (RTL only)</li>
+
+          <li><code>`ReadiumCSS-ruby_pref.css`</code> (CJK only)</li>
         </ol></li>
 
         <li><code>ReadiumCSS-fs_normalize.css</code></li>