feat(newserver): add Xonotic

[Hornochs]

Description

Adding Xonotic as supportes Server

Fixes #3936

Type of change

• Bug fix (a change which fixes an issue).
• New feature (a change which adds functionality).
• New Server (new server added).
• Refactor (restructures existing code).
• Comment update (typo, spelling, explanation, examples, etc).

Checklist

PR will not be merged until all steps are complete.

• This pull request links to an issue.
• This pull request uses the develop branch as its base.
• This pull request subject follows the Conventional Commits standard.
• This code follows the style guidelines of this project.
• I have performed a self-review of my code.
• I have checked that this code is commented where required.
• I have provided a detailed enough description of this PR.
• I have checked if documentation needs updating.

Documentation

If documentation does need updating either update it by creating a PR (preferred) or request a documentation update.

• User docs: https://github.com/GameServerManagers/LinuxGSM-Docs
• Dev docs: https://github.com/GameServerManagers/LinuxGSM-Dev-Docs

Thank you for your Pull Request!

[Hornochs]

Any feedback if I need to do something? @dgibbs64 @glowacki-dev @intel44

[dgibbs64]

I will take look and review it. Thanks

[dgibbs64]

Completed my review and contributions to get everything up to standard. Non Steam servers normally require some extra work. Thanks for your contirbution

[Hornochs]

Thank you very much for your time and effort completing this PR ❤️. I‘m happy that I was able to give a little start and make it possible for LinuxGSM to add this Arenashooter.

Can‘t wait to install it with LinuxGSM 😊