Add compare button to duplicates in Citation relations tab

[harshithap2000]

• Added a "Compare" button for duplicate entries in the CitationRelationsTab.
• Implemented functionality to open a dialog for comparing duplicate entries.
• Enhanced UI to include the compare button alongside the existing "Jump to entry in library" button.

This PR addresses issue #11192.

Mandatory checks

• [ ] Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
• [ ] Tests created for changes (if applicable)
• [ ] Manually tested changed features in running JabRef (always required)
• [ ] Screenshots added in PR description (for UI changes)
• [ ] Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• [ ] Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[koppor]

The real diff is follows:

[calixtus]

Hi @harshithap2000 thank you very much for your PR. Welcome to JabRef programming. Your changes are a great start for your PR. We made some review comments. Please adress them and don't forget to make a screenshot before and after your changes.

[calixtus]

Please also don't remove the section about the Mandatory checks in the comment for a PR, we have them there for the reason, that every contributor should remember that these checks have to be taken care of and kept in mind before creating a PR.

[koppor]

Closing this PR due to inactivity :zzz: Please ping us if you intend to resume work on this one.