Update modal settings in doc

Author: jlukic

server/documents/modules/dimmer.html.eco

@@ -452,9 +452,9 @@ themes      : ['Default']
       </thead>
       <tbody>
         <tr>
-          <td>opacity</td>
-          <td class="six wide">auto</td>
-          <td>Dimmers opacity from 0-1. Defaults to <code>auto</code> which uses the CSS specified opacity.</td>
+          <td>useFlex</td>
+          <td class="six wide">true</td>
+          <td>Whether dimmers should use flex or legacy positioning</td>
         </tr>
         <tr>
           <td>variation</td>

server/documents/modules/modal.html.eco

@@ -844,6 +844,11 @@ themes      : ['Default', 'Material']
           <td>true</td>
           <td>If set to false will prevent the modal from being moved to inside the dimmer</td>
         </tr>
+        <tr>
+          <td>useFlex</td>
+          <td>'auto'</td>
+          <td>Auto will automatically use flex in browsers that support absolutely positioned elements inside flex containers. Setting to true/false will force this setting for all browsers.</td>
+        </tr>
         <tr>
           <td>autofocus</td>
           <td>true</td>