feat: migration tooling docs

[DeagleGross]

Adds migration tooling documentation which is being actively developed at a moment

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Internal previews

📄 File	🔗 Preview link
docs/orleans/migration/guide.md	docs/orleans/migration/guide
docs/orleans/migration/tooling.md	docs/orleans/migration/tooling
docs/orleans/toc.yml	docs/orleans/toc