erp5_run_my_doc: add 'add new' button when editing the last slide

bt5/erp5_run_my_doc/SkinTemplateItem/portal_skins/erp5_run_my_doc/slideeditor.gadget.js.js

@@ -225,14 +225,25 @@
         type: 'button',
         'class': 'list-btn ui-icon-th ui-btn-icon-left',
         text: translation_dict.List
-      }),
+      })
+    );
+    if (disable_next) {
+      button_list.push(
+        domsugar('button', {
+          type: 'button',
+          'class': 'display-new ui-icon-plus-circle ui-btn-icon-left',
+          text: translation_dict['New Slide']
+        })
+      );
+    } else {
+      button_list.push(
         domsugar('button', {
           type: 'button',
-        disabled: disable_next,
           'class': 'next-btn ui-icon-forward ui-btn-icon-left',
           text: translation_dict.Next
         })
       );
+    }
     return button_list;
   }