Add dfn url for Capability: Platform name (#1921)

Author: yezhizhen

index.html

@@ -1514,7 +1514,7 @@ <h2>Capabilities</h2>
  </tr>
 
  <tr>
-  <td>Platform name
+  <td><dfn data-lt="platform name">Platform name</dfn>
   <td>"<code>platformName</code>"
   <td>string
   <td>Identifies the operating system of the <a>endpoint node</a>.
@@ -2078,7 +2078,7 @@ <h3>Processing capabilities</h3>
       <div class=note>
        <p>The following platform names are in common usage with
         well-understood semantics and, when <a>matching
-        capabilities</a>, greatest interoperability can be achieved by
+        capabilities</a> for <a>platform name</a>, greatest interoperability can be achieved by
         honoring them as valid synonyms for well-known Operating
         Systems: