Need to flag external links

We are legally required to flag every link that references an external resource. While this can be done for the few links on our link page it gets rather tedious with our publication list, let alone any other links hard-coded elsewhere.

Can this be done automatically via some (conditional?) CSS or page/view rendering tricks, for instance?

Every external link should be preceded by 🔗 (HTML: #128279, can't paste UTF-8 here!)