Document the 'chromatic.config.json' configuration file and update GitHub Action docs

[ghengeveld]

Explains the use of chromatic.config.json, updates the config options table, removes the config table from the GitHub Action docs (referring to the generic table instead) and adds a chapter about versioning the GitHub Action.

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[github-actions]

🚀 Deployed on https://deploy-preview-configuration-file-and-action-docs-5b99904--chromatic-docs.netlify.app

[domyen]

Thanks! This looks good to me. I committed some typo fixes.

@ghengeveld When does the config file officially roll out and which version of Chromatic CLI supports it?

[ghengeveld]

@domyen Support for chromatic.config.json was added in 7.2.0. We haven't set an "official" rollout date but I think that's where we're at.

Note I was mistakenly referring to chromatic.json but that should be chromatic.config.json. I fixed that now.