Add latex2unicode formatter for displaying previews

[jjsfernandez]

Bibtex entries with characters with diacritics {"a} were not rendering properly when showing non-default previews (eg: IEEE).

I added a call to the LatexToUnicodeAdapter on the "pipeline" when translating the data from the BibEntry to the HTML format to be displayed by the preview pane. With this change every preview style should always handle special diacritics. check issue #5779 for more details.

Here is a screenshot of the IEEE preview of the following entry

@book{Wickman2009non,
author={Wickman, Per-Olof and Persson, Hans},
title={Naturvetenskap och naturorienterande {\"a}mnen i grundskolan: En {\"a}mnesdidaktisk v{\"a}gledning},
publisher={Liber},
address={Stockholm},
year={2009},
ISBN={978-91-47-05333-9},
}

I also added a test to verify this functionality in the future, but the Tests for CitationStyleGenerator are disabled because an unrelated issue, when that issue is fixed the test should work just fine.

• Change in CHANGELOG.md described (if applicable)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (for bigger UI changes)
• Checked documentation: Is the information available and up to date? If not: Issue created at https://github.com/JabRef/user-documentation/issues.

[Siedlerchr]

Thank you very much for your contribution!
Looks good to me. And thanks also for providing a test.
Merry Christmas or Happy Holidays!