feat: Add GitHub governance files

[dronefreak]

Added Governance & Contribution Files

• CONTRIBUTING.md – Explains how to contribute code, report issues, and propose features.
• CODE_OF_CONDUCT.md – Defines expected behavior for all contributors.
• SECURITY.md – Explains how to responsibly report security vulnerabilities.
• CHANGELOG.md – Maintains a history of notable changes per version following Keep a Changelog.
• SUPPORT.md – Provides guidance on where and how to get help with the project.
• GOVERNANCE.md – Describes project decision-making, roles, and maintainer authority.

Updated pre-commit config

• Added MD204 to be avoided in markdownlint-cli to avoid dissecting repeated additions (for example in CHANGELOG)

[lfagotbouquet]

I would prefer to add uv in a separate PR and to try to remove pip when doing it, WDYT?

I have the feeling that adding uv but continuing to rely on pip isn't really the proper way to use uv even if it's of course possible.

[lfagotbouquet]

Also I think the README.md file is still relying on pyenv right?

[lfagotbouquet]

It's a bit unclear if the governance files are intended for the template (i.e. for the projects done from the template) or the template repo itself.
I think it's more for the projects based on this template but if it's for the template repo itself it's a bit relevant because for the moment we can't have maintainers (I think we need an organization account for that and if we can have one freely I will try to do so).

In any case I think we should clarify it somewhere.