Add compare button to duplicates in Citation relations tab

[AbdAlRahmanGad]

I think it would be nice if we added a compare button to the duplicates in the citation relations tab.
The compare button will open the "Possible duplicate entries" window.

It will look something like this:

For more context:
The duplication detection in the citation relations tab was implemented in this PR #11186

[koppor]

@AbdAlRahmanGad Nice idea! Helps to see if JabRef works right - and also helps to add missing data to JabRef (if available)