Improve documentation for the prettier-move plugin

[Sceat]

Description

This PR explains how to use the prettier-move plugin through npm for a package.json workflow, along with CLI usage for direct formatting

npm run prettier

# or
npx --yes prettier@3.3.2 --plugin "$SUI/external-crates/move/tooling/prettier-move/out/index.js" --write "path/to/move/folder/**/*.move"

Test plan

Manually testet

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Name	Status	Preview	Comments	Updated (UTC)
sui-docs	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 23, 2024 5:59am

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