feat(plugin-npm): add npm provenance support (#6750)

## What's the problem this PR addresses?

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Hi! I added support for provenance to `yarn npm publish`.

Closes #5430

## How did you fix it?

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Adapted code from npm to produce a provenance signature in supported CI
environment.

## Checklist

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- [x] I have read the [Contributing
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## Next steps

- Update
https://github.com/npm/documentation/blob/c2efb649816e27d37b37da2b21200e4c9ade0d17/content/packages-and-modules/securing-your-code/generating-provenance-statements.mdx?plain=1#L124

Author: GauBen