[MINOR] Add support for ebdb links

[hokreb]

I have seen, that it is now possible to display citations as nodes, which is kind of impressive to get relations between mentions of literature/papers worked on.

I think it would be also very useful to add a posibility to show up links to entries of the ebdb (contact data base for emacs, an rewrite of bbdb) in the same way. One could easily use this as a kind of small contact relation management tool. As I am neither firm in elisp development nor in the structure of org-roam/org-roam-ui I actually don't know how easy or difficult this would be.