make treemacs-visit-node-in-external-application work like enter on remote files

[JonatanSahar]

When calling visit-in-external... on a remote image, nothing happens, while when just vising it with enter the file is copied over and opened in emacs.
It would be great to be able to do the same with the default system viewer..
Thanks!

[stale]

This issue has been automatically marked as stale because it has not had recent activity (this bot only works as a reminder, it will not close issues).