Fix IPv6 support for the Docker container

[utf-4096]

Description

#1837 introduced a new NGINX config for Docker inspired by the existing contrib/nginx/cinny.domain.tld.conf, but without the listen [::]:80; directive, which breaks the container for those that use IPv6.

This PR adds the IPv4 and IPv6 listen directives to make it work on both again. (I also reformatted the file to follow the project's style).

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

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[utf-4096]

I have read the CLA Document and I hereby sign the CLA

[github-actions]

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[kfiven]

Thanks for fixing this!