Add a "view as BibTeX" option before importing an entry from the cita…

[JamseBonde007]

Add a "view as BibTeX" option before importing an entry from the cita…tion relation tab #11826

This PR implements the feature requested in issue #10869. It adds a button that allows users to display a dialog showing the full BibTeX entry when importing citations from the Citation Relation tab. This enhancement will help users decide whether to import a potentially "duplicate" record by allowing them to see the full details of the entry in BibTeX format.

Closes #11826

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.

[JamseBonde007]

Thank you for your feedback! I've addressed the issues you pointed out and made the necessary changes. Please take a look and let me know if everything looks good now.

[JamseBonde007]

Thank you for the feedback and the tips! I've addressed the comments and reviewed the code in IntelliJ. Please take a look at the updates and let me know if everything looks good.

[JamseBonde007]

Fixed

[Siedlerchr]

From my point of view looks good!
Thanks for the contribution

Please resolve the comments you addressed, makes it easier for us to see which ones you fixed etc

[Siedlerchr]

@JamseBonde007 Thanks for your contribution!