Bring back .mailmap

[koppor]

for gource, we need a .mailmap.

The mailmap we once removed works fine to generate a nice video (see https://github.com/JabRef/jabref/actions/runs/15404094999)

Follow-up to #13230

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• [.] Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• [.] Tests created for changes (if applicable)
• [.] Manually tested changed features in running JabRef (always required)
• [.] Screenshots added in PR description (if change is visible to the user)
• [.] 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.

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

[Siedlerchr]

missing entries e.g. my name

[koppor]

missing entries e.g. my name

Could you tell me your name, please? I think, there is a huge mistake then in .mailmap?

``
Christoph Schwentker [email protected]
Christoph Schwentker [email protected] [email protected]

[Siedlerchr]

Ah now I see it. Sorry, probably saw a commit earlier