Add info about PostgreSQL 18 macOS installer

Author: devrimgunduz

templates/pages/download/macosx.html

@@ -65,6 +65,10 @@ <h3>Platform support</h3>
     </tr>
   </thead>
   <tbody>
+    <tr>
+      <td>18</td>
+      <td>13+ (amd64), 13+ (arm64)</td>
+    </tr>
     <tr>
       <td>17</td>
       <td>11.x (amd64), 12.x (arm64)</td>