chore(core): add license information

site/plugins/admin/lang/en_US.yaml

@@ -250,3 +250,4 @@ admin_twig_debug: "Debug"
 admin_twig_charset: "Charset"
 admin_twig_cache: "Cache"
 admin_published_at: "Published at"
+admin_licence: "Licence"

site/plugins/admin/views/templates/system/tools/information.html

@@ -23,6 +23,10 @@
             <td>{{ tr('admin_web_server_php_interface') }}</td>
             <td>{{ php_sapi_name }}</td>
         </tr>
+        <tr>
+            <td>{{ tr('admin_licence') }}</td>
+            <td><a href="https://github.com/flextype/flextype/blob/master/LICENSE.txt">The MIT License (MIT)</a> Copyright (c) 2018-2019 <a href="https://github.com/Awilum">Sergey Romanenko</a></td>
+        </tr>
     </tbody>
 </table>
 {% endblock %}