Fix addition of new members that did not sync in subfolders.

Author: comintern

Rubberduck.Core/Navigation/CodeExplorer/CodeExplorerCustomFolderViewModel.cs

@@ -133,6 +133,7 @@ protected override void SynchronizeChildren(ref List<Declaration> updated)
                 }
             }
 
+            children = children.Concat(subFolders).ToList();
             AddNewChildren(ref children);
         }
     }