fixed pagetree-count width

packages/app/src/styles/_page-tree.scss

@@ -50,6 +50,7 @@ $grw-pagetree-item-padding-left: 10px;
       }
 
       .grw-pagetree-count {
+        width: 23px;
         padding: 0.1rem 0.3rem;
         font-size: 12px;
       }