Added option to copy the DOI to the copy sub-menu

[AidanM11]

Adds the feature requested in
Fixes #7826

• Modelled off already existing "Copy title" and "Copy key" features
• Adds method copyDOI to CopyMoreAction and binds it appropriately
• Adds new item in RightClickMenu
• Adds appropriate tests to CopyMoreActionTests
• Adds appropriate localization entries
  Screenshot:
  

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• 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 documentation: Is the information available and up to date? If not created an issue at https://github.com/JabRef/user-documentation/issues or, even better, submitted a pull request to the documentation repository.

[calixtus]

Thank you for your interest in this issue, especially for thinking of the tests.
Please do not forget to check the other checkboxes in the pr description too.

[AidanM11]

I've completed the checklist, and everything seems right. The only problem is the checkstyle test failing, saying that there are 5 trailing spaces in CHANGELOG.md, but my change doesn't appear to add any trailing spaces. I'm not sure what to do to fix that.

[Siedlerchr]

Variabl names should be all lowerCamelCase, e.g dois

[Siedlerchr]

Overall looks good, just one minor nitpicking.

[Siedlerchr]

Thanks for the quick follow up. Looks good from my side.
PS: For the next time, it's better to use a separate branch instead of main to avoid unnecessary conflicts. And use something like Fixes ...for autoclosing the issue.

[calixtus]

Looks good to me too, one thing that could be improved in a future PR is making the executable binding dependant on if there is a doi present.

[calixtus]

Thanks for your contribution to JabRef!