Fix HTTP Method for Create Window

The HTTP Method for Create Window command was specified
as POST at https://w3c.github.io/webdriver/#endpoints,
but as GET at https://w3c.github.io/webdriver/#create-window.
Since this command takes a parameter, it needs to use POST method.

Author: JohnChen0

index.html

@@ -3245,7 +3245,7 @@ <h3><dfn>Create Window</dfn></h3>
   <th>URI Template</th>
  </tr>
  <tr>
-  <td>GET</td>
+  <td>POST</td>
   <td>/session/{<var>session id</var>}/window/new</td>
  </tr>
 </table>