docs(training): Docathon

[JPXKQX]

Description

• move general contributing guidelines to main anemoi docs and link here
• restructure user guides, e.g. for building training configs
• closes Dead link in user guide #166

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)
• Documentation update

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📚 Documentation preview 📚: https://anemoi-training--201.org.readthedocs.build/en/201/

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📚 Documentation preview 📚: https://anemoi-graphs--201.org.readthedocs.build/en/201/

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📚 Documentation preview 📚: https://anemoi-models--201.org.readthedocs.build/en/201/

[FussyDuck]

All committers have signed the CLA.

[VeraChristina]

There are broken links and a few unclear references in the user guide (e.g. a reference to "Getting started" but no "getting started" section) -- planning to fix these later today, before merging. cc @HCookie

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I fixed all internal links I could find, and got rid off sentences that referred/linked into nowhere (when I couldn't find where they were supposed to link to).

The user guide could use some more restructuring but I think this is out of scope for this PR. I think we can merge (so that we don't block other PRs that want to add documentation) and do other changes later