[css-writing-modes] Added UTR50 changes to Changes section

Author: kojiishi

css-writing-modes/Overview.html

@@ -2436,6 +2436,7 @@ <h3 class="no-num heading settled heading" id=changes-2012050><span class=conten
   <ul>
     <li>Added back <span class=css data-link-type=maybe>digits</span> value of <a class=property data-link-type=propdesc href=#propdef-text-combine-horizontal title=text-combine-horizontal>text-combine-horizontal</a> and tightened up rules for compressing text.
     <li>Various fixes/clarifications to orthogonal flows.
+    <li>Updated references to UTR50 and how this specification use its values.
   </ul>
 
   <h3 class="no-num heading settled heading" id=changes-201205><span class=content>

css-writing-modes/Overview.src.html

@@ -2470,6 +2470,7 @@ <h3 class="no-num" id="changes-201205">
   <ul>
     <li>Added back ''digits'' value of 'text-combine-horizontal' and tightened up rules for compressing text.
     <li>Various fixes/clarifications to orthogonal flows.
+    <li>Updated references to UTR50 and how this specification use its values.
   </ul>
 
   <h3 class="no-num" id="changes-201205">